Looks like a lot of ink wasted on a visualisation which is of limited benefit to the consumer, and likely to result in lost revenue for the retailer, as people become more aware of how much they are spending on particular product categories.
Not all receipt printers are thermal, however: a lot are thermal-transfer, that uses heat to transfer ink from a film to the paper. That stuff looks much better, and lasts much longer than the crappy thermal-printed receipts.