multiple tax rates across a state

[jima13]

I am currently setting up a web site and everything is going fine except for the tax part. I already have set it up to charge a 2.9% tax rate for everyone in Colorado where I live. The problem gets more complicated though because of how the rates are set up in Colorado.
I'm in a suburb of Denver, Co and the way taxes are done here is they vary a lot by location. For example if someone isn't in Colorado I collect no sales taxes. If they are in the state but outside of the Denver metro area in general I collect the flat sales tax rate of 2.9%. Then if they are in the Denver metro depending where they are I have to collection taxes for a stadium tax plus a transporation tax which adds up to around 4.1%. Then if they are in the same county as me they are another .9% of so and then if they are in the same city as me another 3% or so.
Often it is confusing because it's hard to know where the stadium and transportation tax can be. It's not necessarily by city or county in the metro area and some cities if they are in the right area they may be in the same county as me but also could easily not be. I would set up by zip code but some zip codes for example may be in the same county as me, others aren't.
How would I set up something like this? I'm sure some other states have a similar situation and it seems like this is a problem others likely have come across and it seems to have to be some solution. It should be automated and would be hard to have to manually calculate and to additional payments for taxes.

[especial]

There is no automated or built-in method for charging per-county taxes in the current version of Zen Cart.
However, there have been discussions and beta contributions floating around on the forum dealing with similar issues for California and New York. You might find some ideas in those discussions.
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