Question about setting up multiple tax zones

[markw10]

I am setting up a store now and since I live in Colorado have already set up the Tax Zone for Colorado for 2.9% sales tax.
Here is where I need extra help. The city I am in I have to collect an additional tax of almost 4%.
Also, there is a cultural/entertainment/transportation district that has around a 1.5% tax rate.
There is also a county tax for the county I'm in that is around 1.2% and I will try to find a map to see which zip codes fall completely in that.

The problem with the above transportation district and county tax is there are some zip codes that are 100% in the city but a few that are partial. What I plan to do is simply put the ones that are 100% in the zone in my tax zone and put a disclaimer in a tax section on my web site saying what the tax rates are and that we will have to collect additional taxes if necessary. My idea is most of the time if it's a small purchase it won't be worth it but if it's a larger purchase it's in writing and I can hopefully through Authorize.net do an additional charge to the card. I am new to Authorize.net so I'm not sure if that is possible through virtual terminal or if I would have access to the card number.

Here is what I want to do:
1. I want to have an additional zone for the city I'm in. It's a small city with few if any zip codes that fall completely within the city. What I think I want to do is simply set it up so that if anyone enters the city I am located in it will add that tax zone but the question is how do I set up a tax zone for a city? I only see the tax zones in the setup by State.

2. For the county and the transportation district I need to set up two additional tax zones and obviously they are by zip code. The county may consist of around 10 zip codes, and the transportation district of maybe 30 zip codes or so. How would I set up zones for these and could I set up a zone called transportation district and include all those zones in that one zone.

Thank you for help with the above questions.