That's precisely why I don't ever accept the bribe. If I don't like the non-discounted price, then I don't buy it. Now they neither get the data nor the sale.

What's frustrating is that a lot of grocery stores do this. If you sell something absolutely necessary, such as basic foods, you should not be allowed to do the whole "mark it up to mark it down" strategy.

Also, a tip for most grocery stores (at least in the US): enter in any area code plus 867-5309. Chances are high that somebody has registered it. It's better than sharing with a family member because so many people are using it, the data becomes less useful.

Alternatively, ask the clerk to "use the store card". Usually, they will oblige.