Re: as a regular customer ...
I've only ever seen perishables reduced to a decent price and by a decent percentage (considering they can't be sold after the store shuts that day) in the Co-ops near me. Admittedly the percentage thing is down to the fact that they've become a decent price from the full Co-op price, but it bloody works — marked down around 1500, reduced shelves empty by closing.
(That said, sometimes Co-op's "reduced to clear" prices strongly imply that they understand neither the concept "reduced" nor "to clear").
Near me there are also some Tescos (the crappy overpriced convenience ones), a Morrisons, an M&S and an Aldi. Their reductíons are so slim as to be practically nonexistent and seem to be a waste of yellow stickers as well as the stock they're presumably lobbing into the skip every night. Morrisons is by far the most egregious; you can count on a full fridge unit absolutely overflowing with meat, dairy, ready meals, snacks, fruit and veg right before closing every single night. Reductions are usually a few pennies at best. I hope the staff get to take it when they close.