Can I afford to save this much?

Don't worry, I'm not starting a finance or debt blog. It's just that I was shopping in Sainsbury's the other evening, and according to my enormously long till receipt, I "saved" £9.54. Apart from the slightly churlish thought that they could at least have rounded the discount to £10, I'm not sure about the marketing. Does this mean I'm Sainsbury's nightmare customer, hitting the special offers and the 2 for 1s, or have I just fallen into their little trap and done exactly what they wanted me to do - bought more stuff?

Certainly I can't afford to make savings like that every time I go shopping. In my defence, the fridge and cupboards had got rather bare, and I did need to get some food...