All of the major supermarkets give loyalty card points (other than when special promotions apply) at a rate which (nominally) gives you back 1% of what you've spent. The actual figure is slightly lower because they don't give points on 'parts of pounds'. For example, if you spend �0.90, �1.76, �4.78 and �10.96 in successive transactions, you'll get 0p, 1p, 4p and 10p (= a total of 15p) back. Whereas if you buy all of the goods in one transaction (�18.40) you'll get 18p back.
Each cooperative society divides out its profits between its members annually, so dividend rates can vary. In their most recent dividend statement, my local society (East of England) paid back 2.5% of what each member spent during the preceding year. Their system doesn't allocate 'points' (or pennies) for each transaction; it simply adds up all of your purchases and pays out 2.5% of the total. So, unlike the major supermarkets, 'parts of pounds' still earn money.
Chris