In the United States, there are only six states that do not have sales taxes. For someone who is travel from a state with no sales tax to one of the states with sales taxes, it can sometimes get confusing. After all, you are used to paying the price that is marked, and sometimes may even have the exact change ready for the cashier, only to have to dig into your pocket or purse for more money.
Of course, sometimes it can happen in reverse as well when someone from one of the states with sales taxes visits a state with no sales tax. In addition, it can become difficult for someone who travels to different states because the rates are different. Until you learn the rates for the different states you visit, there will also exist the confusion. You will eventually become used to the taxes in the states you visit the most and be able to know before you finalize your purchase how much you will need to pay.