Depends on the platform. If you're using an eCommerce site, I usually plug in something like Avalara Tax which handles collection, real time rates, and remittance and stuff, but it's pretty expensive. If you're trying to do it on the cheap(er) and easy...find a payment provider who is the "merchant of record" (Example: Square). The merchant of record is required to pay the tax so you don't have to deal with it at all, but you'll usually pay some sort of revenue share for that.

Or you can just be a crazy person and setup business licenses everywhere.