Of course a store manager can look up purchase records "without reason" or, more accurately, for any reason, including curiosity or to make sure there was no violation of store policy. The purchase records *from* the store are the *store's* records--which means that legally, an employee or manager of the store can look them up. Maybe he is violating store policy, and if you think he is, you can certainly bring that up to his boss or supervisor (assuming he is not the highest-level employee or owner), but legally, he as the right to do this.