If ya live in a state with sales tax, then odds are you have a 'use tax'. It's the state's way of collecting sales tax on items bought out of state, or over the i-net where the seller doesn't have a b&m facility in the state being shipped to. It's based on the 'honor'

system in most cases, though many states don't make a point of trying to inform the public about it's existence.
So technically if it becomes an issue & they can track an out of state purchase via whatever means, see that you didn't pay sales tax, and didn't send them their cut, they'll politely ask you for it.

That's what the latest flak between Amazon & the State of Texas I believe it is was. Texas wanted Amazon to collect sales tax, Amazon said ' we ain't got no stinkin' facility in Texas, collect it yourself'.
Hope that helps.