Even/odd pricing. It's part of economics. People tend to think it's a good deal if you sell it for .99c instead of $1.00. It's very effective in clearing out product or making a sale. Companies aren't necessarily being greedy, but as they are for-profit businesses, the even/odd pricing makes the product more attractive for purchase. Another strategy: something like 2 for $3.00. It makes you feel like you're getting a deal, at least compared to running them $1.50 each.
I work retail, and put some of our excess stock on an in-store sale. I'm amazed at how often slapping a tag on a product with barely a drop in the price will make it fly off the shelf. From what I see, you almost can get by with putting a tag on it and let the consumer mentality take flight. "Oooh, there's a tag! We're saving $$$$$$!" when they're simply saving a few pennies.
Short answer: it's the way business is done because in order to stay in business, you must turn a profit.