Need more information. Insulating against the cold? Protection from humidity? Bugs? Critters (mice and the like)? Is the garage heated? Forced air? Space heater? Size of garage? Will vehicle emissions be a consideration?
I would not store tobacco in the garage. However, if you must, use a cooler, since they are well insulated against the cold and the heat. Rick Newcome stores his tobacco in a cooler, however, his cooler is in the closet in his house.
If it gets that cold that the tobacco might freeze, no insulation in the world would matter. After several hours, the inside temp is going to match the outside temp anyway without some sort of internal heater (like a light bulb).