In the auto insurance business, a motor vehicle is termed a "total loss" if the either the car cannot be repaired or if the cost to fix the vehicle is near or more than the actual cash value of the automobile.
Some people buy back this totaled vehicle (and get a salvaged title) or if they have no insurance to repair the "totaled" vehicle keep it without making repairs.
A rolling total is slang term meaning a car that still gets around but should be destroyed and taken off the road such as cars that are totaled by an insurance company. Since this is a slang term it may not necessarily refer to cars that were actually totaled out vehicles but can also apply to cars that look old and raggedy or work so poorly that a person may call this type of car in this condition a "rolling total."
Thus if your friend called your car a rolling total they would be saying that it is in disrepair and looks as if it should not be on the roadway.