If a vehicles is registered in two names can you use it as a tax break on two tax returns

It depends on what you're claiming.  If you're claiming the auto registration fee -- a single fee for an auto used by two people -- then only one person can claim that fee.  However, if you're claiming work-related mileage, then each person can claim the mileage that he/she put on the car.

So the car itself could reasonably appear on two different tax returns, but you can only claim the specific business mileage that you yourself put on.