Following up after talking to my CPA in case anyone else is interested...
"Remember the email I sent out in late June regarding the Supreme Court ruling on sales tax nexus? The bottom line is sales tax will now be charged on every product in every state, regardless of where you buy it from. This even applies to software that is downloaded and not necessarily tangible. The states have been hurting for revenue for a long time because of places like Amazon, so this ruling levels the playing field so that all businesses, whether they be Internet retailers or traditional brick-and-mortar, will now be required to charge sales tax on everything they sell. When it comes to things like software, you get charged based on your domicile, not where you accept the download."
So... no Montana road trip for me