I think some of the southern turnpike is still under the ticket system, you get a ticket when you enter and don't pay until you exit or reach the plaza where the ticket system ends. At that plaza all booths are manned, so exact change is not needed. Even on the section that has regular toll plazas, manned booths are available, look for the green signs. I would say tintub's estimate of 3 hours is optimistic, it would probably require maintaining an average of over 80mph, the posted limit is mostly 70.