Yes as the sales tax rules vary from state to state. The interesting thing is historically I think sales tax was only for physical goods if you download the software there is no sales tax but if you get a physical CD then its taxed. Some states have modified the laws but many like California still don't tax downloaded software.
For what it's worth VAT isn't uniform across the EU either. IIRC the EU specifies minimums, but countries are allowed higher rates and can manage their own exclusions too.
It can get even more complicated here because you can have a county and/or city sales tax add-on so sales tax can vary from city to city.. Doesn't matter to much until you get into big purchases like cars that people starting buying cars in the lowest tax cities. So then the state starting requiring that the tax to be calculated to the address where you are registered.