I just use a GPS map system with an "avoid tolls" option (in my case a Garmin stand-alone unit, but I assume the "avoid tolls" option is available in some phone-based mapping systems too), and I never end up on toll roads. In fact, in the rare cases where something has a toll in only the opposite direction, I sometimes have to turn the "avoid tolls" off temporarily just to be able to get on a road or bridge which only has a toll in the opposite direction. So it's a bit overzealous, but it definitely shields me from tolls.