Tax by city

I need to be able to set the tax rate for California, US to 7.5% but just the city of San Diego, California to 8%. There isn’t a break down of cities in the tax settings, so I realize this would require an edit in the plugin.

So can I get some help with where and how to edit that? And also, can I submit this as a feature request because there’s obviously different taxation in different areas of a state. I’m not sure zip code would be the best solution because there can be many different zips per city also. But it’s probably more worth the time to enter all the zips to a custom tax field on the settings page than worry about the customer maybe mispelling their city name.

Any help on this would be very appreciated.

https://wordpress.org/plugins/wp-e-commerce/