But, Jon, doing a little research I see that Massachusetts has a 5% sale or use tax. If you buy goods out of state, or online, which are intended for use, storage, or consumption within Massachusetts, you are required to pay a 5% use tax on those goods. If the same goods are purchased in a U.S. state that does collect sales tax for such goods at time of purchase, then whatever taxes were paid by the purchaser to that state can be deducted (as a tax credit) from the 5% owed for subsequent use, storage or consumption in Massachusetts.
See:
http://en.wikipedia.org/wiki/Use_tax