You can raise prices with buyers or sales (sales preferred, since buyers usually buy below price so someone will have to make another suggestion once there's a sale if you raise with buyers). You can lower prices with sellers that have been listed for more than 1 day (i.e. not a quicksell). You can't raise with sellers because then someone could list something for 100 keys while no one else was selling it, doesn't mean it should be 100 keys. You can't lower with buyers because someone could list something for 1 scrap while no one else was buying it, doesn't mean it should be 1 scrap. You can lower with sales only if you have proof that it was listed for more than 1 day (i.e. not a quicksell), but usually it's easier to just use sellers.

Less than 5% though, for this item price change must be at least 0.22. You also forgot to link item histories for classifieds sellers used as proof and buyer profiles for buyers used as proof (usually just one or the other, depending on whether you're raising or lowering).