POS software records each sale when it happens, so your inventory records are always up-to-date. Better still, you get much more information about the sale than you could gather with a manual system. By running reports based on this information, you can make better decisions about ordering and merchandising.
You can analyze sales data, figure out how well all the items on your shelves sell, and adjust purchasing levels accordingly.
You can maintain a sales history to help adjust your buying decisions for seasonal purchasing trends.
You can improve pricing accuracy by integrating bar-code scanners and credit card authorization ability with the POS system.