I am not sure of the laws of MA as I am in texas, I only read about MA as a particilar state that has been having issue with it so I used it as an example. I am not sure you are right though about sales tax being paid at registration. If I own a car for 10 years and move to MA and register the car in MA, MA is not going to charge me sales tax. I think you may have another tax you are thinking of.
In Texas, you pay TTL (tax, title, license) when you buy the car, not when you register it (You do pay some taxes for road work and such, which is part of registration, but that is not sales tax). So if say oklahoma did not charge tax when you bought the car, but texas does. I could go to Oklahoma, buy the car tax free, take it back to Texas and register it. Since Texas does not charge sales Tax when you register the car, I just got a car tax free. By law since my state has sales tax, I must remit that tax when I file taxes. If I do not, I am guilty of tax evasion. The same applies to any good, not just cars. Technically if you go from MA to New Hamshire to buy booze, you have to remit that tax as well but no state is going to chase a few bottles of Captain Morgan.
The same applies to a phone. If you buy a phone from a state that does not have sales tax, that company wont charge you tax. But if you buy it and imidiately import it to another state that does have sales tax, you are supposed to remit that tax to the state.