I'd pay the ticket, as Tuneman1984 says - if you don't pay immediately you will get hit in two ways;
1 - Hertz will take the money from your credit card plus a admin charge of around $50 (In the UK it is £30)
2 - The parking fine will probably increase due to the non-payment (or if there is an early payment discount you would lose it)

Effectively you are going to have to pay the fine anyway, so, get it dealt with without including Hertz and it will be cheaper and easier.