The most common strategy of most Germans I know is to simply put everything into the cart after it's scanned, move the cart towards the car and dump everything into some sort of carry box in the trunk. Carry that box (or boxes) into the house at home and put the stuff you bought wherever it is stored.

If I shop by bike I usually have a backpack that I brought for shopping open at the cashier and dump everything in it upon scan.

One time use bags are sort of faded out. There's no more free bags (I think). Makes ecological sense imo.