The simple solution, for a listen-only use anyway, is to program them in with no tone (or CSQ) since that will pick up anything on the channel, tone or not. They can then use whatever tone they want and you'll still pick them up. No need to use tone search or program in several channels for the same frequency but different tones.
Now if you're planning to attempt to talk to them (and why is that?), you'll need to use the correct tone, but that will probably just get you in trouble and removed from the store. Sure, the FCC won't care, but chances are that your local WalMart will have a lot more pull with the local PD than you will and they will most certainly not care that you may be legally using your MURS radio the store will claim (probably correctly) that you were interfering with their private communications. While they probably won't be able to charge you criminally, they can have you removed and given a criminal trespass warning, which will allow them to arrest you and charge you with violating that notice if you go to the store again.