[[I am in FLA this week and tonight was out on a cashless toll road and didn't realize it until I was on the toll road. Should I tell Hertz tomorrow when I return the car or will they just charge my credit card when the notice from the state comes in?]]

"They'll just charge your credit card, no need to do anything. It's spelled out in the rental agreement."

Nope. At Hertz you have to sign up for $4.99 per day for the rental period for the transponder/license tolls (not sure of the maximum), and THEN your cc will be charged by a 3rd party for the tolls (plus an "administrative fee" which is unknown). If you are only driving around the MCO area (not south) you can just not bother, but be sure to go through the cash lanes.