Yes, we should use the comparative “fewer” instead of “less” for countable supermarket items like bars of soap, pieces of lamb chop, bottles of ketchup, and pieces of banana or orange; and we should use the comparative “less” for uncountable items like flour, rice, salt, water, and dishwashing fluid. That’s the prevailing English grammar rule. However, it has become traditional practice for many supermarkets to write “10 items or less” instead of the grammatically correct “10 items or fewer” on the signboards for their limited checkout counters. (I suppose the thinking behind this is that the noun “item” is indefinite anyway as to whether it’s countable or uncountable, so why make a fuss with the choice of comparative?) At any rate, there seems to be no stopping the practice now, and I don’t think there’s any chance that this errant usage can be legislated out of existence. Still, it remains advisable to correctly use “fewer” and “less” all the time in our own written or spoken English; after all, the ability to discern the semantic difference between these two comparative adjectives marks a person as a truly educated English speaker.
