Round up prices on the aisles before chopping into our change at the tills

I am amazed that once again we are getting ripped off with this new system of rounding up & yet we are just allowing it to happen. Today I was in three different supermarkets & each one basically stole my money.

The first by taking 3c from me, the second took 2c even though I had the correct change to give them but they refused to take it from me as they said they are ‘rounding up’ & then the third by taking 4c of my money.

Surely if they are trying to do away with small change would it not just make more sense for the stores to ‘round up’ their prices before we get to the till?