Walmart is using the MURS frequencies... You'll usually find them on 154.6000, 155.5700 or 151.6250 mHz
Use this link and just program all of these in your scanner and next time you go to walmart you'll probably find them come up on one of them. All of the walmarts here where I live are using 154.6000 mhz. http://wiki.radioreference.com/index.php/MURS
154.570, 154.600 are common ones. I don't think there is a standard though. I understand some are using 460 MHz freqs and there was a posting a while back about Walmart going digital with new spread spectrum digital encrypted radios Pretty sad when Walmart comms are more secure than local PD's.
Walmart in CT (at least New Haven, Hamden, and Branford) are in the 154.000 mhz range. They use motorola XTN Radios. Ray my wife works at the New Haven store so I'll tell her we come looking for you if she hears remarks bein made on the channel-LOL
I'm the corporate alarm tech for the state of NJ - most of my stores use only blue or green dot, and they don't bother with PL unless they're in a large shopping complex with other retailers.
There are a few that have rented higher-class business-band Moto's with PL's, but most of them all use the XTN's They buy 'em bulk from our Sam's Club's via an MTR (merchandise transfer request).
I have to coordinate with management when I do my annual fire inspections, and let me tell you, the women 5X more than the men literally EAT the HT when they talk (and I carry a personal MTS2000, and they can be cranked up a little TOO loud some times... )