I've not seen those before, then again I can't remember the last time I was in Walmart, certainly the grocery side. Canadian Tire has them, or at least used to, and I found that half the time they didn't work.
It seems it's a skill daddy didn't teach me. I just got back from grocery shopping. I opted for boxes this time (they're free). Turns out I'm just as bad at boxing! The poor checkout staff have such a pained look on their faces watching me.
I don't want to distract you from using regular checkouts.........
But just as an FYI.
Heavy stuff at the bottom; where possible, square/rectangular stuff at the bottom.
Position items to 'open the bag', making it easier to load everything else.
Irregular shapes, mid-weight go next, light, and fragile on top.
Multiple fragile items (prone to getting squashed), give'em their own bag.
Ideally everything frozen together, everything needing refrigeration w/frozen or together on its own.
Non-vac-packed meat in its own bag (avoids cross-contamination, should be separate from anything you might consume raw, so produce, and breads etc.)
*****
Personally, I prefer self-checkouts, as I'm faster than most cashiers/lines.
With the notable exception if I have large number of items that require codes (typically produce or bulk); as I need to look those up, and that adversely impacts by timeliness.