Yes, definitely worth sterilising. Before the campervan we have been known to have a caravan (please don't shoot me, OK?). We used our own hose to fill up from water supplies rather trust other campers to be hygenic. One year we switched to a transparent rubber hose and I was horrified at the start of the next season how much green mould had cultivated itself inside. Yuk. So very definitely use sterliser on the tanks, and try and change those fill-up hoses if you can't see through them. Best to put the steriliser in your clean tank and then run it through to the grey water tank so that it fills the internal connector pipes as well. (Top tip to clean a short hose - tie a small piece of cloth to a long piece of string, pass the string through the hose and then pull the wet cloth through. )
