I haven't noticed and - when it comes to Tesco at least - I keep an eye on them. It's amazing how many errors you can find on the receipt; usually an offer that 'didn't go through'. When I complained, I was told the pricing system was in India or somewhere far-flung. I replied by saying that may well be, but it's strange how the errors always seem to be in Tesco's favour. Check your receipt!
Back in March multi-buy offers were largely cancelled to discourage stock-piling and panic buying. I am not sure to what extent they have come back.
Bit in general I find Supervalu worse at applying offers - current highly advertised offers especially.