Of course, I think sales tax conflicts happen because they are an ill-defined problem. If I go across the border and buy a durable good from an appliance store (or any other good), I will pay the sales tax for Illinois even though I am transporting it back to Wisconsin. I can't say I'm taking it to a different state and not pay sales tax..
Interestingly enough, that's not even true in every state. In Washington state, if you are buying a durable good, have ID from a state that charges 3% sales tax or less, and say that you will be using it in your home state, then the retailer is not required to charge sales tax. (They may not be *allowed* to charge sales tax, I don't remember precisely.) They do this because they have so many neighboring states with low sales tax rates (OR, ID, AK) that retailers would lose too much business otherwise. (Yes, I know Alaska isn't technically 'neighboring' but when Alaskans want to go down to the lower-48 and do some shopping, they generally go to Seattle.)