Leo, as a former resident of Taxachusetts, AKA, Massachusetts, the use tax is essentially Massachusetts way of trying to get money from consumers who drive to New Hampshire to buy merchandise. New Hampshire does not have sales tax so if you live in Boston and want a 60 inch television set to watch the Superbowl you could drive to Best Buy in Watertown MA and pay $500 and then pay an additional $31.25 in tax or spend $5 in gas and drive to and from Salem N.H. (about 50 miles round trip) to the Best Buy there and save the $31.25 minus $5 for a grand savings total of $26.25. While in N.H. you can get liquor cheaper and cigarettes (if a smoker) at half price and.....well, a lot of money can be saved. Long story short, it is up to the tax goons to track you down. Technically one is suppose to save receipts and declare the tax savings on your income tax form. I suspect no one does it. Massachusetts is no dummy and they do tax people who purchase a car in a state with no sales tax (i.e., N.H.). Buy a car in N.H. and you will pay Mass tax on the car. Massachusetts does allow tax payers to voluntarily pay a higher state income tax rate if they want to do so-- I am not sure anyone does so.
Another wrinkle to sales tax, as I understand it, is if a store exists in your state and you buy from the store of the same chain in another state. you have to pay sales tax. L.L. Bean is a great example. Here in Kentucky there is no L.L. Bean store so if I buy from Beans (located in Maine) I do not pay sales tax. Back in Massachusetts I would have to pay sales tax as there is a L.L. Bean store there. Of course I could drive to Concord NH to the Bean store there and not pay sales tax.
Then there are the Indian cigarette stores in New York. They sell cigarettes via mail/UPS and do not charge any form of tax. A lot of states got perturbed by that and actually went after buyers. I recall talking with a few folks in Chicago when I lived there who bought cigarettes from the tribes and were hit with tax bills from the state of Illinois. Guitar strings are one thing, cigarettes are another.
be true to the one you love but have many flings with different guitars