I believe that there is no sales tax bought in other states via the internet UNLESS the company has a presence in your state. Most companies like Amazon add the sales tax automatically based on your zip and the company you are buying from.
A law was passed by Congress in the 1950’s that prohibited states from requiring companies to collect sales tax, or pay income tax on merchandise shipped into a state when the shipper has no presence in the recipient state. What the states do is impose a nearly unenforceable use tax on the purchasers.
However, states are interpreting “presence” ever more broadly. If you ship by postal service or common carrier, you don’t have a presence, but if you deliver in your own vehicle, you risk having it impounded at the state border, because most states interpret that as having a presence.
Furthermore, the states are also sliding through a loophole in the law for services, taxing services performed in another state for a client in the home state, and, some are even attempting to tax merchandise sent to a state that has no sales tax.