I remember a story a few years ago where someone was complaining about a similiar situation. They set up a infrared camera and found out someone they knew was siphoning their gas.
Amongst my skills are such diverse elements as fear, surprise, ruthless efficiency, and an almost fanatical devotion to the Pope, and nice red uniforms - oh damn!
Actually, the movement is toward doing away with registers completely. RFid tags on the products and scanners at the doors, all tied together with wifi and a credit card you set up in your phone gets charged.
If you have them in your area, check into "Piggyback Movers". We used them to move my Mom up here from FL. They were definitely the least expensive, but you'll need to wait until they have a full load headed to your new area.