If it has never had water in it, then sanitizing isn't necessary - it's the stagnant water that causes the bacteria/algae/etc, to grow in a tank.
However, I agree with valhalla360 that it wouldn't hurt to fill, drain/run through pipes, then fill again - to get any dust, sawdust, etc, out that might have gotten into the tank or pipes. It will also let you check for leaks before you head out on your trip.
As to sanitizing in general, some folks do some don't. I only sanitize right after I buy a used RV (don't know what prior owners do) and then only if I notice a change in the smell/taste of the water. However, I don't normally leave my tank filled for long periods of time unused. My logic in regards to "I don't/do drink from the tank" is that if I am washing the dishes, utensils, glassware, cookingware, etc, then I expect the water to be potable. If I'm only using it to bathe in and/or the toilet, then I don't need it to be potable.
