Cashless payment systems like E-ZPass have helped make highway driving a less irksome experience by speeding up lines. Rental car companies even offer this option so you don’t have to worry about an embarrassing last-minute scrounge for change at the tollbooth, but rental car customers are now realizing that this convenience can come at a huge price.We’ve previously told you about some of the steep fees involved in using a rental company’s toll-paying device, but those fees could be small change compared to penalties for drivers who use the car’s device without even realizing it.The Pew’s Stateline recently took a...