Colorado expatriate here:
You’re right, the sales tax is very confusing. You have to realize that what you call “Denver” is really a Metro Area, of which the city of Denver is a relatively small part. It is comprised of several municipalities: Denver, Westminster, Littleton, Lakewood, Englewood, Arvada, Aurora, Thornton, Northglenn, Wheatridge ( I think I got them all). These cities have different sales tax rates on consumer goods.
Each of these cities has further breakdowns into districts such as Federal Heights, Commerce City, Columbine, Greenwood Village, Cherry Creek etc. These districts may also have additional taxes for things like road improvement districts, school district levies, flood management levies and so forth.
To further complicate the issue, the metro area spans four counties: Denver, Jefferson, Adams and Arapahoe. Each of these counties has a different sales tax and some cities are in two counties (ex. Arvada is in Jefferson and Adams counties) so the sales tax rate will be different from one city block to the next.
Also, if you weren’t already tearing your hair out, there are different taxes for home-consumption food than for other goods and different taxes still for prepared foods and these rates vary by County.
So. You could expect to pay 6.3% on goods purchased in Thornton or 8.31% on the same goods purchased in Arvada/Adams County. I would budget and plan on 8% and the plus/minus eventually balances to that average if you shop around the Metro Area.
Hope that helped. Here’s an ibuprofen tablet for you.