I call BS anyway. There are only 50, is it too much to have some schmoe simply look the damned tax up on a sheet of paper? WTF?
If only it were so simple. The US sales tax system is a byzantine mess. You have state taxes, city taxes, transit authority taxes, public improvement fees, etc which apply based on where the sale occurred. That is the easy piece though. The difficult part is that the tax rates themselves can be different based off the products. Some products are taxable in one state but not in others. A simple example is plain bottled water which is pretty much untaxed everywhere, and flavored bottled water which is taxable in most states. Then you have tax free holidays where a certain class of products are tax free for 3 days (typically back to school), but it is a different set of days for different areas of the country of course.
To top all that off, cities, states, etc are constantly changing the rules as to which products are taxable and which are not. It is a real pain in the a** to deal with, but all of the national retail chains have to deal with it, so why can't Amazon and the other online retail companies? The best case would be to just have a national sales tax that is the same everywhere instead of the current stupid system. Instead of forcing companies to devote millions of person hours to figuring out what taxes to pay, people could actually be doing something productive.