Note that going through the city would also have Google route you on the Skyway which is $5.30. You can also pay via credit card.
Alternatively, you can also just blow through the tolls and pay missed tolls online later by entering your rental car license plate number, dates/times of passage through toll plazas. Your rental car agency will try to charge you for the tolls, but if you have evidence that you paid, you can submit that and they will (or should) waive the toll and service charges. It's more effort, but it's another option.