I'm simply not going to sell anything to anyone in Colorado that is not picked up at my physical retail location. Yeah, I'm gonna lose a few customers on the western slope and down south that I have been shipping to for years, but the additional time and brain damage every month makes it prohibitive to calculate and collect the appropriate tax. According to one news item I saw, there is over 650 separate sales tax collecting entities in the state of Colorado. I am not aware of any resource that can tell a retailer the correct tax entities for any give street address. Add in the complication of the billing address not being the same as the delivery address (gifts, or having stuff delivered to your work). This is going to be even more of a nightmare for online retailers such as Amazon.