Go to Bulma's Skill Shop and leave. As soon as she says, "Come again, okay?", press and hold L2. Keep entering and leaving while still holding L2, and your item percentage will be steadily increasing. You can save these capsules by either buying something or equipping just one of the capsules you cheated for on one of your characters. You may have to do it a lot to get the last 1%. This is best done with the volume on "mute", since Bulma's voice gets really annoying.
As added by "A good gamer", sometimes the capsules you gain will go away. To keep them, you must purchase an item at the capsule shop. This will save the game and retain your capsules.
Submitted by: Stephen Krokowski