If you always have beer on tap, then you don’t need to clean as often, but if you intend to shut your system down for any length of time, it’s a good idea to clean the lines and tap tower with a sanitizer. Here is a good page describing how to clean you beer tapper system and associated cleaning products.
How and When to Clean: Beer Line Cleaning
Cleaning Products: Beer line Cleaning Products
Also see: Cleaning Instructions.