Ok I don't understand how using that peg board with colored cards is any easier than simply ticking marks on a piece of paper.
For example, if you don't reach 100 cards on a peg and want to know how many are there, you still have to count them individually, since you only make 1 tick every 100 cards when the peg is full.
On the other hand, if you simply tick the standard 4 lines and a cross for every 5 sales on a piece of paper, and space them in fixed rows of 10, you can quickly count the total.