every business with a Web presence will have to incorporate 50+ different tax rules based on customer location
This has come up before, with Internet-based catalog sales. IIRC, there's more like 7,200 different tax rules to apply. Certainly around here there are different city tax rates in the nearby cities. My wife is looking into starting a small store, and as we're outside the city limits she would only have to calculate the state sales tax and not state+city sales tax.
Fundamentally, there may be no basis for anything.