The software would have to work everywhere. The tax collections (review/enforcement, really) process only has to work in one place. Tax law in one place is usually clear enough; the complexity is in the aggregate.
My state doesn’t have to give a rip that NYC has a city surtax on this but not that, or that some other jurisdiction treats clothing items up to $100 as non-taxable while we put the limit at $175.
My state doesn’t have to give a rip that NYC has a city surtax on this but not that, or that some other jurisdiction treats clothing items up to $100 as non-taxable while we put the limit at $175.