I had something like this happen to me. I got a parking ticket at a meter on the street in the city of Philadelphia. I paid the parking ticket. Then the rental car agency tried to fine me for the ticket after I had already returned the car. I told them that I had already taken care of the ticket, and they required me to fax them a copy or some proof that I had paid the ticket. So then I had to get the city of Philadelphia to mail me something that stated that I paid the ticket in order for the car rental agency to stop harrassing me for the fine. It took a lot of phone calls and time to get this straightened out, but any violation with a rental car is a headache. Be careful when you rent.

Don't pay the rental agency anything until you take care of the fine through the proper channels rather than through the car rental agency. I won't put my trust or money on them to do what's needed.

Sorry this information is after the fact, but if this sort of thing happens again--let's hope it doesn't--I would wait for the actual fine from the toll road agency before dealing with the car agency.