Stock in accounting problems?

It seems to me that your boss has not acquired a software system sophisticated enough to capture info on purchases and sales. If you sell a large variety of items, there's no way you can do it manually and still be accurate. You need to have a POS system that is integrated with a stock module so that each time you sell something, you just scan the barcode or key in the code on the cash register keypad and the items sold will be updated in the sales and inventory modules.