It’s an imperfect solution. VPNs are an issue - and even if you don’t use a VPN, the API only knows the location of the ISP’s servers - which can be in a different state.

My point was that, the law should leave tax inclusion in pricing as optional. There is no way to implement automatic detection cleanly, other than prompting the user to confirm their location, which is a huge annoyance - so the ‘tax inclusion’ rule would not make things better or more convenient.