It is not my responsibility to collect taxes for Colorado.

That said. Taxes should only be collected at the place of sale, not point of delivery. Taxes support the community in which a store is located. If that jurisdiction does not have a sales tax, it collects other ways. My purchase is paying for someone's income which is taxed in that jurisdiction. Colorado does not pay for the sewer, water, roads, ect in those jurisdictions, nor does general fund money pay for the roads that deliver said purchase.

Tracking out of state purchases is an undo burden on us. I never keep receipts, so if they want to audit me, the burden is on the state to show I owe sales taxes.