Ordering by rolls Selling individually

A sticker store has to order their items in rolls (200 stickers in each roll) but has to sell them individually. On their PO they cannot select individual stickers with the quantity being 200; they have to select a single roll. What is the best way to do this and keep track of inventory by knowing how many stickers are left in a roll? I tried using matrix items but when its time to create a PO the system forces you to select the individual dimensions. Any suggestions are greatly appreciated.