Honest question, what sort of process does it look like for you to total everything up? Do you keep running totals or do it at the end of the year? Do you have an accountant? Would you prefer that online stores collected for you?
Usually I'd use a combination of my Mint records (which had convenient totals for each online merchant, of which I really only used 5 or 6 in a typical year) and the Massachusetts safe harbor law (which essentially allowed me to assume that I spent 1% of my AGI on untaxed purchases less than $1000, and pay use tax based on that number). If I bought anything online or out-of-state that cost more than $1000, I'd add that in separately, but that happened rarely enough that it was pretty hard to forget how much I spent on those items.
What we have right now is a situation where some stores collect taxes in some states. As a consumer, I would prefer it if all stores collected taxes for all states, for three reasons. First, I wouldn't have to figure out which stores already collected taxes, so it would save me time. Second, because I like seeing how much I'm going to pay for something, taxes included, at the time of purchase. And third, because I believe that taxes should be levied fairly and consistently, and that would put online stores on the same footing as brick-and-mortar stores, and honest taxpayers on the same footing as people who are inclined to see what they can get away with.
As a startup founder, however, I'm less enthusiastic. The process of filing taxes in all 50 states would be a huge burden. If a national sales-tax clearinghouse existed, it would be a different story, but under the status quo, it's just too much paperwork for a small company to handle.
