Nah, you only map to a single PTT, and those are then mapped internally to state tax codes. i.e. you say "its diapers" and we then go "it fits in this band in D

Nah, you only map to a single PTT, and those are then mapped internally to state tax codes. i.e. you say "its diapers" and we then go "it fits in this band in Des Moines, this band in Culver City, this band in Podunk, etc.". As to having to do it for every product - nope - we allow bulk flagging of any datum against products by category or product metadata. Sure, there's manual work there, but there's no additional requirement for any of our merchants, as they've already got this data in place for the appropriate calculation of tax rates when they're shipping intra-state. If we didn't have it set up this way, our some of our customers with millions of SKUs would have man-decades of work ahead of them!