Companies find it more profitable to increase prices (above the sale price) by a larger amount on an unpredictable basis than by a small amount in a predictable way. Customers find it trouble some to avoid unpredictable price increases -- and may not even notice them for lower-value goods -- but easy to avoid predictable ones...
Have you noticed that supermarkets often charge ten times as much for fresh chili peppers in a package as for loose fresh chilies? That's because the typical customer buys such small quantities that he doesn't think to check whether they cost four cents or forty. Randomly tripling the price of a vegetable is a favorite trick: customers who notice the markup just buy a different vegetable that week; customers who don't have self-targeted a whopping price rise.
I find these pricing strategies pretty interesting, and I can verify that they happen from my work on pricing strategy with an unnamed company that is headquartered in Atlanta. Now as opposed to more comments on why you think corporations are evil for such tactics, I would like to see a good reasoned comment on why this is not an "evil" thing to do, pehaps even other ideas of how to price along these lines, or other pricing strategies you or your parents may have noticed at the grocery store.
Source: Marginal Revolution