I've had to pay online after using the toll roads in Illinois and not having change to do so. It's not fun to have to remember the relevant exit number/location and time/date and have to get around to doing it, but with real-time maps and a quick screenshot, I make my own record at the toll booth and then catch up online at the airport or my destination to pay up. I've yet to mess up this.
IL and driving to ORD is probably the primary reason why I still lug around a whole bunch of coins.