Wait, the business doesn't pay the sales tax, they collect it from the customers and pass it on to the State. If you live in a city that borders another state, you cross the border and buy something in the neighboring state, you don't pay sales tax to your own state. The store collects it for the State you are making the purchase in, not the one you call home.
Good luck figuring out how much to collect when states like California have dozens of different tax rates.
Also, have fun trying to setup accounts with each state, some that require large fees or deposits to open a sales tax account.
You don't just shove the money you collect in an envelope and drop it on the mail.
I work for a small company that sells software not just in different states, but in other countries.
We had to pay for additional software that integrates into our accounting system to track the sales tax in each state, and it's a mess dealing with all the different rules in each state.