I think just about every state that has a sales tax law can collect sales taxes on stuff bought from out of state and shipped in, it is just that most don't do it because enforcement would be about impossible. But if you look in a lot of mail order catalogs, they have the state sales tax rates listed and say to enclose the proper amount. The money is returned to the state from which the product was ordered.
My wife used to work for a company that made and sold steel building joists and trusses. One of her jobs was finding out the proper sales tax to charge out of state customers and forward the money quarterly to the various states. Of course, that was big bucks, but the size of the order really doesn't matter unless the law sets a minimum.
Even so, I agree that if the smith sets a specific rate, then that should include whatever charges are involved, other than shipping.
Jim