There's no federal sales tax, including for products transferred to you over communication channels. There is a federal gasoline tax of a fixed amount per gallon purchased. There are also (relatively low) federal taxes on the use of interstate communications facilities.

Some states claim they will charge a sales tax on "digital" products, but in currently have no way to enforce the tax since they cannot send state agents to take property from residents of other states.

Some states say they will charge a "use tax" to their residents who purchase anything in another state but take delivery in their home state. You are supposed to report this kind of purchase to your home state. They generally can force you to pay this this it if they know about the purchase. This is the subject of the proposed "internet tax" on items purchased and delivered across state lines. It's not clear how this could be a state sales tax, but will likely be coordinated and collected by the feds (agents will be able to take your property) with some kind of controls to make the tax the same for residents of all states.

Oregon, New Hampshire, and Delaware have no sales tax on any purchases by their residents. Some do have high income tax rates to offset the lack of a sales tax.

It's possible to live in Washington (no state income tax) and purchase items in Oregon (no sales tax) and live mostly tax free. Lots of people live across the river from Portland OR in Vancouver WA to make this practical (at least until Obama's trolls decide to start collect a toll on crossing the river with stuff you bought in Oregon .

I arranged a couple of chip shows in my state of Oregon and dealers did not have to report or pay sales tax on transactions at the show.