Walmart has those little insulated paper bags in racks at either end of the frozen food aisles. If you take a bunch of them to the checkout counter and ask that they pack your cold things in those bags, they will do that (and if they don’t, you have a little conversation with management). And to help them make a distinction between canned foods and squishables, you can put enough distance between the groups of foods to be noticed even by the densest of checkers. Not to mention, when you get stuck with one who really has no concept of why your bread shouldn’t go underneath a bag of apples, you can peek in the bag and exclaim with dismay, “oh no, darnit, that loaf of bread is all squished. I hadn’t noticed this before. Would you mind calling someone to go and exchange this one for an unsquished loaf? Thanks so much, I really appreciate it.” *Smile*. For people who work under time pressure, paying attention to bagging things right is a much lesser evil than having the whole process held up for 5 minutes or more while another employee has to go and get the customer a replacement for what got damaged in the bagging process.