A transferring dealer cannot charge you sales tax on an out of state sale. If he attempts, find an honest dealer.
A dealer in central Virginia got away with this for years before the revenue people started snooping. He was not authorized to collect sales tax and did not remit any of the taxes he collected to the state. He was convicted of a felony.
Every state is desperate for money and will try to collect use taxes on out of state purchases. I now live in TN. They have a compact with all adjacent states to report sales over a certain threshold to each other. A lot of folks here drive to NC to buy households full of furniture. The dealer in NC will not charge sales tax IF the merchandise is delivered to a common carrier. However he is obligated to report sales of out of state shipments to his tax authorities who share this with other compact states.
If you live in such a state, you can expect to get a reminder of sales taxes due if you make such a purchase. The threshold is several thousand dollars.
I could tell tales for hours about being audited by sales tax auditors in serveral states. I fear them more than state income tax or fed auditors.
Again, the dealer is a crook. Report him to your sales tax authorities. I guarantee that he did not remit it to the state, but pocketed it. As someone explained above, there is no mechanism for him to collect a tax unless he reports a sale, which he cannot because the sale occurred out of state.
As an aside, I was once tasked with determining how to assess and collect sales taxes for an internet company the did business in almost every county in the country. It's not possible, you can't go below the state level with any degree of accuracy and could not possibly know of the additional sales taxes imposed by transit authorities, townships, cities, villages, and counties. The company involved with this gave up on the idea, which was a dumb one to start with.
As another interesting aside, jewelers and furriers in NYC, for years, would make a sale over the counter to a customer in their showroom. Clearly this transaction was subject to lots of taxes imposed by the city and state of New York. To get around this, the dealer would hand the item to the customer but mail the empty box to the customer's home address if out of state. This created the illusion that the transaction was a routine sale to an out of state customer. The "item" was delivered to a common carrier and delivered out of NY, thus exempt from NY sales taxes. After a number of well publicized stings, dealers are reluctant to do this now.
I live in TN which has a sales tax of 9.25%. Evading sales tax has been raised to an art form by residents. Internet sales are very popular of the most mundane items like light bulbs.