I wonder if this extends to county/city taxes? That would open up even more ridiculous complexity.

Locally, there's a poorly structured (ie not machine-readable) spreadsheet of municipal taxes that tell you, based on _what side of the street_ you're on, whether you fall under the "mosquito district tax" that requires a small percentage more sales tax to pay for the annual spraying of mosquitoes.

Without simplifying the tax codes, I'm not sure full compliance over the web is even possible...