I think some companies are playing it better-safe-than-sorry. I had better not get charged sales tax on any of my boxes, but that's because I live in a no-sales-tax state, and if a company is trying to charge me sales tax, I would question how well they truly understood what they do and do not collect taxes on, and that would lead to me thinking that they don't know how to run their business or that they're just a bunch of shady creeps.
But. I do know that consumers (at least in Washington state) are technically required by law to pay sales tax when bringing purchases that were not taxed at the time of purchase. If you buy a car (for example) in Oregon and live in Washington, you pay the sales tax when you license your car. If you buy a computer, jeans, cat food, a washing machine, or anything else that Washington state considers taxable, you are technically supposed to pay sales tax on it even though you bought it in Oregon. I think the technical term is use tax since it's not collected at time of sale. You're still supposed to pay it. Very few people even know of this law, though, and even people who *do* know about it have no clue how to track and pay these taxes, so pretty much the only time anyone actually pays the sales tax on an Oregon purchase brought into Washington is when it's a car, and that's pretty much only because of the documentation involved in licensing it. There was a chunk of time (late '80s? early '90s?) when there was a crackdown on people buying cigarettes (huge amounts, like probable resale quantities) at Costco in Portland and then driving back home to the Washington side. More than one person got pulled over for speeding, got mouthy with the cop, and ended up with a ticket for not paying taxes on the cigarettes that had a higher fine attached than the speeding ticket.
ANYWAY. Teal deer. I should have gone to bed an hour ago. I sometimes get the feeling that some of these companies have decided that they will just start charging the sales tax now and submit it to the recipients' states just to get ready for the future since it seems destined to happen.