I always give Salem my car sick hound one ginger pill prior to getting in the car. I can't honestly tell you if it helps or not, but it doesn't hurt. She hasn't had any adverse reaction, although I also don't give it daily. I vote why not give it a try for a few days and see how it works.
I remember an episode of Myth Busters where they tested all the crazy theories to combat nausea and ginger was the only one that really tested effective, seems like that could translate to the dogs.
Goodluck!