5mm isn't a lot but I wouldn't go back to that shop again. I'd call them and let them know. They will probably claim that it won't affect how they ski, and they may be right. Ski them and try switching skis without paying attention to which ski is mounted back. If you can't tell then live with it. If the shop isn't willing to give you a new pair I'm not sure it's worth getting them remounted since the new holes would be so close to the old holes.
You could also them to mount a different pair of bindings which will have a different hole pattern and ask for some money back or store credit for your troubles.