I, as a Vermont resident, have purchased vehicles three times from out of state dealers (first time, New Jersey, second time, Pennsylvania, third time, New Hampshire) without getting a Vermont title or paying sales tax before driving the car home. In NJ & PA, I did not pay NJ or PA sales tax, and NH has no sales tax.
In both instances, I was issued a "manufacturers certificate of origin" by the dealer, and issued a temporary plate from the state where the dealer was located. I drove the car home, then went to my Vermont DMV with my "certificate of origin" and my sales documents indicating what I paid for the car. I paid Vermont sales tax directly on the purchase price of the car, got a registration and plates, and the Vermont title followed in the mail from Vermont DMV.
I realize other states may work differently.