At Dixons in the UK (when I briefly worked there 10 years or so ago) the pence were used in a similar way to signal things to floor staff. For example, IIRC, prices ending .98 signalled a discontinued product.
Additional staff signalling was provided by messages on price tags. For example, 'please ask if you need help' meant 'high-margin, high-commission item', whereas 'have you remembered your spares and accessories?' meant 'low-margin, low-commission, item'.
Working part-time in retail at Staples Canada, I can tell you that all of our prices ending in $x.97 or $x.x7 are clearance; and therefore subject to an additional discount if there is a current promo going on.
As for the random prices, I have no idea. Although it does make it easier when doing prices changes for flyers, because in each section, no two products have the same price (cent wise).
Additional staff signalling was provided by messages on price tags. For example, 'please ask if you need help' meant 'high-margin, high-commission item', whereas 'have you remembered your spares and accessories?' meant 'low-margin, low-commission, item'.