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          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_PuertoRicoMunicipalSecuritiesMarketRiskMember" xlink:label="loc_nstfip_PuertoRicoMunicipalSecuritiesMarketRiskMember_200645" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_PuertoRicoMunicipalSecuritiesMarketRiskMember_200645" use="optional" order="34" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_RecentMarketConditionsMember" xlink:label="loc_nstfip_RecentMarketConditionsMember_200664" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_RecentMarketConditionsMember_200664" use="optional" order="35" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_ReinvestmentRiskMember" xlink:label="loc_nstfip_ReinvestmentRiskMember_200646" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_ReinvestmentRiskMember_200646" use="optional" order="36" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_RestrictedAndIlliquidInvestmentsRiskMember" xlink:label="loc_nstfip_RestrictedAndIlliquidInvestmentsRiskMember_200684" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_RestrictedAndIlliquidInvestmentsRiskMember_200684" use="optional" order="37" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_SpecialRisksRelatedToCertainMunicipalObligationsMember" xlink:label="loc_nstfip_SpecialRisksRelatedToCertainMunicipalObligationsMember_200647" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_SpecialRisksRelatedToCertainMunicipalObligationsMember_200647" use="optional" order="38" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_StructuredProductsRiskMember" xlink:label="loc_nstfip_StructuredProductsRiskMember_200685" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_StructuredProductsRiskMember_200685" use="optional" order="39" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_SwapTransactionsRiskMember" xlink:label="loc_nstfip_SwapTransactionsRiskMember_200648" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_SwapTransactionsRiskMember_200648" use="optional" order="40" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_TaxabilityRiskMember" xlink:label="loc_nstfip_TaxabilityRiskMember_200650" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_TaxabilityRiskMember_200650" use="optional" order="41" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_TaxRiskMember" xlink:label="loc_nstfip_TaxRiskMember_200649" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_TaxRiskMember_200649" use="optional" order="42" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_TobaccoSettlementBondRiskMember" xlink:label="loc_nstfip_TobaccoSettlementBondRiskMember_200651" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_TobaccoSettlementBondRiskMember_200651" use="optional" order="43" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_UnratedSecuritiesRiskMember" xlink:label="loc_nstfip_UnratedSecuritiesRiskMember_200652" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_UnratedSecuritiesRiskMember_200652" use="optional" order="44" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_ValuationRiskMember" xlink:label="loc_nstfip_ValuationRiskMember_200653" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_ValuationRiskMember_200653" use="optional" order="45" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_WhenIssuedAndDelayedDeliveryTransactionsRiskMember" xlink:label="loc_nstfip_WhenIssuedAndDelayedDeliveryTransactionsRiskMember_200686" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_WhenIssuedAndDelayedDeliveryTransactionsRiskMember_200686" use="optional" order="46" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_ZeroCouponBondsRiskMember" xlink:label="loc_nstfip_ZeroCouponBondsRiskMember_200654" />
          <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cef_AllRisksMember_200074" xlink:to="loc_nstfip_ZeroCouponBondsRiskMember_200654" use="optional" order="47" />
        </link:definitionLink>
        <link:labelLink xlink:type="extended" xlink:role="http://www.xbrl.org/2003/role/link" >
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_AlternativeMinimumTaxRiskMember" xlink:label="loc_nstfip_AlternativeMinimumTaxRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_AlternativeMinimumTaxRiskMember" xml:lang="en-US">Alternative Minimum Tax Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_AlternativeMinimumTaxRiskMember" xlink:to="lab_nstfip_AlternativeMinimumTaxRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_AntiTakeoverProvisionsMember" xlink:label="loc_nstfip_AntiTakeoverProvisionsMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_AntiTakeoverProvisionsMember" xml:lang="en-US">Anti-Takeover Provisions [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_AntiTakeoverProvisionsMember" xlink:to="lab_nstfip_AntiTakeoverProvisionsMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_BelowInvestmentGradeRiskMember" xlink:label="loc_nstfip_BelowInvestmentGradeRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_BelowInvestmentGradeRiskMember" xml:lang="en-US">Below Investment Grade Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_BelowInvestmentGradeRiskMember" xlink:to="lab_nstfip_BelowInvestmentGradeRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_CallRiskMember" xlink:label="loc_nstfip_CallRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_CallRiskMember" xml:lang="en-US">Call Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_CallRiskMember" xlink:to="lab_nstfip_CallRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_CounterpartyRiskMember" xlink:label="loc_nstfip_CounterpartyRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_CounterpartyRiskMember" xml:lang="en-US">Counterparty Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_CounterpartyRiskMember" xlink:to="lab_nstfip_CounterpartyRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_CreditRisksMember" xlink:label="loc_nstfip_CreditRisksMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_CreditRisksMember" xml:lang="en-US">Credit Risks [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_CreditRisksMember" xlink:to="lab_nstfip_CreditRisksMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_CreditSpreadRiskMember" xlink:label="loc_nstfip_CreditSpreadRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_CreditSpreadRiskMember" xml:lang="en-US">Credit Spread Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_CreditSpreadRiskMember" xlink:to="lab_nstfip_CreditSpreadRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_CybersecurityRiskMember" xlink:label="loc_nstfip_CybersecurityRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_CybersecurityRiskMember" xml:lang="en-US">Cybersecurity Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_CybersecurityRiskMember" xlink:to="lab_nstfip_CybersecurityRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_DefaultedOrDistressedSecuritiesRiskMember" xlink:label="loc_nstfip_DefaultedOrDistressedSecuritiesRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_DefaultedOrDistressedSecuritiesRiskMember" xml:lang="en-US">Defaulted or Distressed Securities Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_DefaultedOrDistressedSecuritiesRiskMember" xlink:to="lab_nstfip_DefaultedOrDistressedSecuritiesRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_DeflationRiskMember" xlink:label="loc_nstfip_DeflationRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_DeflationRiskMember" xml:lang="en-US">Deflation Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_DeflationRiskMember" xlink:to="lab_nstfip_DeflationRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_DerivativesRiskMember" xlink:label="loc_nstfip_DerivativesRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_DerivativesRiskMember" xml:lang="en-US">Derivatives Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_DerivativesRiskMember" xlink:to="lab_nstfip_DerivativesRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_DirectLendingRiskMember" xlink:label="loc_nstfip_DirectLendingRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_DirectLendingRiskMember" xml:lang="en-US">Direct Lending Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_DirectLendingRiskMember" xlink:to="lab_nstfip_DirectLendingRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_DurationRiskMember" xlink:label="loc_nstfip_DurationRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_DurationRiskMember" xml:lang="en-US">Duration Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_DurationRiskMember" xlink:to="lab_nstfip_DurationRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_EconomicAndPoliticalEventsRiskMember" xlink:label="loc_nstfip_EconomicAndPoliticalEventsRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_EconomicAndPoliticalEventsRiskMember" xml:lang="en-US">Economic and Political Events Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_EconomicAndPoliticalEventsRiskMember" xlink:to="lab_nstfip_EconomicAndPoliticalEventsRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_EconomicSectorRiskMember" xlink:label="loc_nstfip_EconomicSectorRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_EconomicSectorRiskMember" xml:lang="en-US">Economic Sector Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_EconomicSectorRiskMember" xlink:to="lab_nstfip_EconomicSectorRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_FinancialFuturesAndOptionsTransactionsRiskMember" xlink:label="loc_nstfip_FinancialFuturesAndOptionsTransactionsRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_FinancialFuturesAndOptionsTransactionsRiskMember" xml:lang="en-US">Financial Futures and Options Transactions Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_FinancialFuturesAndOptionsTransactionsRiskMember" xlink:to="lab_nstfip_FinancialFuturesAndOptionsTransactionsRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_FloatingAndVariableRateSecuritiesRiskMember" xlink:label="loc_nstfip_FloatingAndVariableRateSecuritiesRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_FloatingAndVariableRateSecuritiesRiskMember" xml:lang="en-US">Floating and Variable Rate Securities Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_FloatingAndVariableRateSecuritiesRiskMember" xlink:to="lab_nstfip_FloatingAndVariableRateSecuritiesRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_FundTaxRiskMember" xlink:label="loc_nstfip_FundTaxRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_FundTaxRiskMember" xml:lang="en-US">Fund Tax Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_FundTaxRiskMember" xlink:to="lab_nstfip_FundTaxRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_GlobalEconomicRiskMember" xlink:label="loc_nstfip_GlobalEconomicRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_GlobalEconomicRiskMember" xml:lang="en-US">Global Economic Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_GlobalEconomicRiskMember" xlink:to="lab_nstfip_GlobalEconomicRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_HedgingRiskMember" xlink:label="loc_nstfip_HedgingRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_HedgingRiskMember" xml:lang="en-US">Hedging Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_HedgingRiskMember" xlink:to="lab_nstfip_HedgingRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_IncomeRiskMember" xlink:label="loc_nstfip_IncomeRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_IncomeRiskMember" xml:lang="en-US">Income Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_IncomeRiskMember" xlink:to="lab_nstfip_IncomeRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_InflationRiskMember" xlink:label="loc_nstfip_InflationRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_InflationRiskMember" xml:lang="en-US">Inflation Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_InflationRiskMember" xlink:to="lab_nstfip_InflationRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_InsuranceRiskMember" xlink:label="loc_nstfip_InsuranceRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_InsuranceRiskMember" xml:lang="en-US">Insurance Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_InsuranceRiskMember" xlink:to="lab_nstfip_InsuranceRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_InverseFloatingRateSecuritiesRiskMember" xlink:label="loc_nstfip_InverseFloatingRateSecuritiesRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_InverseFloatingRateSecuritiesRiskMember" xml:lang="en-US">Inverse Floating Rate Securities Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_InverseFloatingRateSecuritiesRiskMember" xlink:to="lab_nstfip_InverseFloatingRateSecuritiesRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_InvestmentAndMarketRiskMember" xlink:label="loc_nstfip_InvestmentAndMarketRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_InvestmentAndMarketRiskMember" xml:lang="en-US">Investment and Market Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_InvestmentAndMarketRiskMember" xlink:to="lab_nstfip_InvestmentAndMarketRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_LegislationAndRegulatoryRiskMember" xlink:label="loc_nstfip_LegislationAndRegulatoryRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_LegislationAndRegulatoryRiskMember" xml:lang="en-US">Legislation and Regulatory Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_LegislationAndRegulatoryRiskMember" xlink:to="lab_nstfip_LegislationAndRegulatoryRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_MarketDiscountFromNetAssetValueMember" xlink:label="loc_nstfip_MarketDiscountFromNetAssetValueMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_MarketDiscountFromNetAssetValueMember" xml:lang="en-US">Market Discount from Net Asset Value [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_MarketDiscountFromNetAssetValueMember" xlink:to="lab_nstfip_MarketDiscountFromNetAssetValueMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_MunicipalSecuritiesMarketLiquidityRiskMember" xlink:label="loc_nstfip_MunicipalSecuritiesMarketLiquidityRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_MunicipalSecuritiesMarketLiquidityRiskMember" xml:lang="en-US">Municipal Securities Market Liquidity Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_MunicipalSecuritiesMarketLiquidityRiskMember" xlink:to="lab_nstfip_MunicipalSecuritiesMarketLiquidityRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_MunicipalSecuritiesMarketRiskMember" xlink:label="loc_nstfip_MunicipalSecuritiesMarketRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_MunicipalSecuritiesMarketRiskMember" xml:lang="en-US">Municipal Securities Market Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_MunicipalSecuritiesMarketRiskMember" xlink:to="lab_nstfip_MunicipalSecuritiesMarketRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_MunicipalSecuritiesRiskMember" xlink:label="loc_nstfip_MunicipalSecuritiesRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_MunicipalSecuritiesRiskMember" xml:lang="en-US">Municipal Securities Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_MunicipalSecuritiesRiskMember" xlink:to="lab_nstfip_MunicipalSecuritiesRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_OtherInvestmentCompaniesRiskMember" xlink:label="loc_nstfip_OtherInvestmentCompaniesRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_OtherInvestmentCompaniesRiskMember" xml:lang="en-US">Other Investment Companies Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_OtherInvestmentCompaniesRiskMember" xlink:to="lab_nstfip_OtherInvestmentCompaniesRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_PuertoRicoMunicipalSecuritiesMarketRiskMember" xlink:label="loc_nstfip_PuertoRicoMunicipalSecuritiesMarketRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_PuertoRicoMunicipalSecuritiesMarketRiskMember" xml:lang="en-US">Puerto Rico Municipal Securities Market Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_PuertoRicoMunicipalSecuritiesMarketRiskMember" xlink:to="lab_nstfip_PuertoRicoMunicipalSecuritiesMarketRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_RecentMarketConditionsMember" xlink:label="loc_nstfip_RecentMarketConditionsMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_RecentMarketConditionsMember" xml:lang="en-US">Recent Market Conditions [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_RecentMarketConditionsMember" xlink:to="lab_nstfip_RecentMarketConditionsMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_ReinvestmentRiskMember" xlink:label="loc_nstfip_ReinvestmentRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_ReinvestmentRiskMember" xml:lang="en-US">Reinvestment Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_ReinvestmentRiskMember" xlink:to="lab_nstfip_ReinvestmentRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_RestrictedAndIlliquidInvestmentsRiskMember" xlink:label="loc_nstfip_RestrictedAndIlliquidInvestmentsRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_RestrictedAndIlliquidInvestmentsRiskMember" xml:lang="en-US">Restricted and Illiquid Investments Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_RestrictedAndIlliquidInvestmentsRiskMember" xlink:to="lab_nstfip_RestrictedAndIlliquidInvestmentsRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="lab_nstfip_RestrictedAndIlliquidInvestmentsRiskMember" xml:lang="en-US">Restricted and Illiquid Investments Risk</link:label>
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_SpecialRisksRelatedToCertainMunicipalObligationsMember" xlink:label="loc_nstfip_SpecialRisksRelatedToCertainMunicipalObligationsMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_SpecialRisksRelatedToCertainMunicipalObligationsMember" xml:lang="en-US">Special Risks Related to Certain Municipal Obligations [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_SpecialRisksRelatedToCertainMunicipalObligationsMember" xlink:to="lab_nstfip_SpecialRisksRelatedToCertainMunicipalObligationsMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_StructuredProductsRiskMember" xlink:label="loc_nstfip_StructuredProductsRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_StructuredProductsRiskMember" xml:lang="en-US">Structured Products Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_StructuredProductsRiskMember" xlink:to="lab_nstfip_StructuredProductsRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_SwapTransactionsRiskMember" xlink:label="loc_nstfip_SwapTransactionsRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_SwapTransactionsRiskMember" xml:lang="en-US">Swap Transactions Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_SwapTransactionsRiskMember" xlink:to="lab_nstfip_SwapTransactionsRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_TaxabilityRiskMember" xlink:label="loc_nstfip_TaxabilityRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_TaxabilityRiskMember" xml:lang="en-US">Taxability Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_TaxabilityRiskMember" xlink:to="lab_nstfip_TaxabilityRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_TaxRiskMember" xlink:label="loc_nstfip_TaxRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_TaxRiskMember" xml:lang="en-US">Tax Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_TaxRiskMember" xlink:to="lab_nstfip_TaxRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_TobaccoSettlementBondRiskMember" xlink:label="loc_nstfip_TobaccoSettlementBondRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_TobaccoSettlementBondRiskMember" xml:lang="en-US">Tobacco Settlement Bond Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_TobaccoSettlementBondRiskMember" xlink:to="lab_nstfip_TobaccoSettlementBondRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_UnratedSecuritiesRiskMember" xlink:label="loc_nstfip_UnratedSecuritiesRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_UnratedSecuritiesRiskMember" xml:lang="en-US">Unrated Securities Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_UnratedSecuritiesRiskMember" xlink:to="lab_nstfip_UnratedSecuritiesRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_ValuationRiskMember" xlink:label="loc_nstfip_ValuationRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_ValuationRiskMember" xml:lang="en-US">Valuation Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_ValuationRiskMember" xlink:to="lab_nstfip_ValuationRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_WhenIssuedAndDelayedDeliveryTransactionsRiskMember" xlink:label="loc_nstfip_WhenIssuedAndDelayedDeliveryTransactionsRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_WhenIssuedAndDelayedDeliveryTransactionsRiskMember" xml:lang="en-US">When-Issued and Delayed-Delivery Transactions Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_WhenIssuedAndDelayedDeliveryTransactionsRiskMember" xlink:to="lab_nstfip_WhenIssuedAndDelayedDeliveryTransactionsRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_ZeroCouponBondsRiskMember" xlink:label="loc_nstfip_ZeroCouponBondsRiskMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_ZeroCouponBondsRiskMember" xml:lang="en-US">Zero Coupon Bonds Risk [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_ZeroCouponBondsRiskMember" xlink:to="lab_nstfip_ZeroCouponBondsRiskMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_CommonSharesMember" xlink:label="loc_nstfip_CommonSharesMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_CommonSharesMember" xml:lang="en-US">Common Shares [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_CommonSharesMember" xlink:to="lab_nstfip_CommonSharesMember" />
          <link:loc xlink:type="locator" xlink:href="nstfip-20260331.xsd#nstfip_InterestAndOtherRelatedExpensesMember" xlink:label="loc_nstfip_InterestAndOtherRelatedExpensesMember" />
          <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="lab_nstfip_InterestAndOtherRelatedExpensesMember" xml:lang="en-US">Interest and Other Related Expenses [Member]</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_nstfip_InterestAndOtherRelatedExpensesMember" xlink:to="lab_nstfip_InterestAndOtherRelatedExpensesMember" />
        </link:labelLink>
      </link:linkbase>
    </appinfo>
  </annotation>
  <import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" />
  <import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <import namespace="http://xbrl.sec.gov/dei/2025" schemaLocation="https://xbrl.sec.gov/dei/2025/dei-2025.xsd" />
  <import namespace="http://www.xbrl.org/dtr/type/2024-01-31" schemaLocation="https://www.xbrl.org/dtr/type/2024-01-31/types.xsd" />
  <import namespace="http://xbrl.sec.gov/cef/2025" schemaLocation="https://xbrl.sec.gov/cef/2025/cef-2025.xsd" />
  <import namespace="http://xbrl.sec.gov/cef-pre/2025" schemaLocation="https://xbrl.sec.gov/cef/2025/cef-2025_pre.xsd" />
  <element name="CommonSharesMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_CommonSharesMember" substitutionGroup="xbrli:item" />
  <element name="InterestAndOtherRelatedExpensesMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_InterestAndOtherRelatedExpensesMember" substitutionGroup="xbrli:item" />
  <element name="AlternativeMinimumTaxRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_AlternativeMinimumTaxRiskMember" substitutionGroup="xbrli:item" />
  <element name="AntiTakeoverProvisionsMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_AntiTakeoverProvisionsMember" substitutionGroup="xbrli:item" />
  <element name="BelowInvestmentGradeRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_BelowInvestmentGradeRiskMember" substitutionGroup="xbrli:item" />
  <element name="CallRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_CallRiskMember" substitutionGroup="xbrli:item" />
  <element name="CounterpartyRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_CounterpartyRiskMember" substitutionGroup="xbrli:item" />
  <element name="CreditRisksMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_CreditRisksMember" substitutionGroup="xbrli:item" />
  <element name="CreditSpreadRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_CreditSpreadRiskMember" substitutionGroup="xbrli:item" />
  <element name="CybersecurityRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_CybersecurityRiskMember" substitutionGroup="xbrli:item" />
  <element name="DefaultedOrDistressedSecuritiesRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_DefaultedOrDistressedSecuritiesRiskMember" substitutionGroup="xbrli:item" />
  <element name="DeflationRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_DeflationRiskMember" substitutionGroup="xbrli:item" />
  <element name="DerivativesRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_DerivativesRiskMember" substitutionGroup="xbrli:item" />
  <element name="DirectLendingRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_DirectLendingRiskMember" substitutionGroup="xbrli:item" />
  <element name="DurationRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_DurationRiskMember" substitutionGroup="xbrli:item" />
  <element name="EconomicAndPoliticalEventsRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_EconomicAndPoliticalEventsRiskMember" substitutionGroup="xbrli:item" />
  <element name="EconomicSectorRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_EconomicSectorRiskMember" substitutionGroup="xbrli:item" />
  <element name="FinancialFuturesAndOptionsTransactionsRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_FinancialFuturesAndOptionsTransactionsRiskMember" substitutionGroup="xbrli:item" />
  <element name="FloatingAndVariableRateSecuritiesRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_FloatingAndVariableRateSecuritiesRiskMember" substitutionGroup="xbrli:item" />
  <element name="FundTaxRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_FundTaxRiskMember" substitutionGroup="xbrli:item" />
  <element name="GlobalEconomicRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_GlobalEconomicRiskMember" substitutionGroup="xbrli:item" />
  <element name="HedgingRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_HedgingRiskMember" substitutionGroup="xbrli:item" />
  <element name="IncomeRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_IncomeRiskMember" substitutionGroup="xbrli:item" />
  <element name="InflationRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_InflationRiskMember" substitutionGroup="xbrli:item" />
  <element name="InsuranceRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_InsuranceRiskMember" substitutionGroup="xbrli:item" />
  <element name="InverseFloatingRateSecuritiesRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_InverseFloatingRateSecuritiesRiskMember" substitutionGroup="xbrli:item" />
  <element name="InvestmentAndMarketRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_InvestmentAndMarketRiskMember" substitutionGroup="xbrli:item" />
  <element name="LegislationAndRegulatoryRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_LegislationAndRegulatoryRiskMember" substitutionGroup="xbrli:item" />
  <element name="MarketDiscountFromNetAssetValueMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_MarketDiscountFromNetAssetValueMember" substitutionGroup="xbrli:item" />
  <element name="MunicipalSecuritiesMarketLiquidityRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_MunicipalSecuritiesMarketLiquidityRiskMember" substitutionGroup="xbrli:item" />
  <element name="MunicipalSecuritiesMarketRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_MunicipalSecuritiesMarketRiskMember" substitutionGroup="xbrli:item" />
  <element name="MunicipalSecuritiesRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_MunicipalSecuritiesRiskMember" substitutionGroup="xbrli:item" />
  <element name="OtherInvestmentCompaniesRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_OtherInvestmentCompaniesRiskMember" substitutionGroup="xbrli:item" />
  <element name="PuertoRicoMunicipalSecuritiesMarketRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_PuertoRicoMunicipalSecuritiesMarketRiskMember" substitutionGroup="xbrli:item" />
  <element name="RecentMarketConditionsMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_RecentMarketConditionsMember" substitutionGroup="xbrli:item" />
  <element name="ReinvestmentRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_ReinvestmentRiskMember" substitutionGroup="xbrli:item" />
  <element name="RestrictedAndIlliquidInvestmentsRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_RestrictedAndIlliquidInvestmentsRiskMember" substitutionGroup="xbrli:item" />
  <element name="SpecialRisksRelatedToCertainMunicipalObligationsMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_SpecialRisksRelatedToCertainMunicipalObligationsMember" substitutionGroup="xbrli:item" />
  <element name="StructuredProductsRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_StructuredProductsRiskMember" substitutionGroup="xbrli:item" />
  <element name="SwapTransactionsRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_SwapTransactionsRiskMember" substitutionGroup="xbrli:item" />
  <element name="TaxabilityRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_TaxabilityRiskMember" substitutionGroup="xbrli:item" />
  <element name="TaxRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_TaxRiskMember" substitutionGroup="xbrli:item" />
  <element name="TobaccoSettlementBondRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_TobaccoSettlementBondRiskMember" substitutionGroup="xbrli:item" />
  <element name="UnratedSecuritiesRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_UnratedSecuritiesRiskMember" substitutionGroup="xbrli:item" />
  <element name="ValuationRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_ValuationRiskMember" substitutionGroup="xbrli:item" />
  <element name="WhenIssuedAndDelayedDeliveryTransactionsRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_WhenIssuedAndDelayedDeliveryTransactionsRiskMember" substitutionGroup="xbrli:item" />
  <element name="ZeroCouponBondsRiskMember" type="dtr-types:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="nstfip_ZeroCouponBondsRiskMember" substitutionGroup="xbrli:item" />
</schema>
