3. Cents are a more common currency than potatoes in the industrialized world. And they're easier to carry.
2. The 9s look like they're spooning, which is comforting.
1. Remember when you were a kid and being able to count to 100 was very impressive? 99 cents gives you that penultimate moment of glory for all eternity.
If I'm going to waste energy on this argument, I'm going to waste it HARD.