a reverse IP lookup should give you a good estimate and you can always ask the user to enter their address for more accurate price.
Not really, no.
Zip codes also aren't great either. A single zip code can cover many different tax jurisdictions, even different states.
Meanwhile, 99% of people will see the price they can expect to pay.
That seems like terrible advice. Oh, the price is $X. And once you've entered all your info "just kidding." I'd much rather know there are some things not included up-front if they're not reasonably factored in.
Or better yet, give municipalities an incentive to stop layering a kinds of taxes. Just have a VAT and be done with it.
Everyone is an edge case in some form. You, included.
Just have a VAT and be done with it.
This just illustrates that you don't understand the that taxes have multiple purposes, and why taxes are the way they are. Attend a few city council meetings.
I bet that's wrong, and that a huge chunk of shopping is from cell phones that usually have an effectively random IP when they're not at their home location.
Switching our tax regime to VATs, effectively flattening 13,000+ sales tax jurisdictions down to 50, would be a monumental undertaking involving rethinking and reorganizing financing of literally everything below the federal level. And in the end it would solve a problem that is at best a minor annoyance to most Americans.
The juice ain't worth the squeeze.