An entrepreneurial programmer or group of programmers could create a database of all state and local sales tax formulas, put it online, and then let small businesses subscribe to it for a small price.
Set it up so a point of sales systems (POS) can log in, automatically put in the buyer’s zip code, the web site computes the tax, and send it back as data to the POS to finish the customers charges.
It wouldn’t take a lot of work, and could make the developers/web site owner lots of $$$.
They key would be to charge very little for a long-term subscription and get lots of subscribers.
Any FReeper programmers out there, feel free to develop my idea, but just give me credit! :->
They do that for shipping costs already.
Large $ accounting systems already have that. The real problem though is that generally each state requires that a quarterly sales tax return be filed. Automate that.