Ceramics with class 2 dielectrics (X5R, X7R, Y5v and so forth) have a significant change of capacitance with DC bias, and for that reason I would normally use a device with a rated voltage of at least double the voltage I am bypassing with this technology.
When using Tantalum capacitors, manufacturers recommend derating devices with MnO2 electrolytes by 50% and to 80% of rated voltage for polymer electrolytes. Tantalums are popular as their CV product density is very high compared to other types.
Aluminium electrolytic capacitors are quite rugged and can be used closer to their rated voltage, but there is a trade-off, mainly in terms of ESR and physical size.
I do not know if your vehicle battery powered system is on the unswitched system in a vehicle (i.e. it is connected to a generator for charging); if so, you would need to withstand very large voltages during load dump