You can set a minimum order price or quantity on your shop. So lets say for instance a customer buys a single product from your website and it cost say £5, you can set the minimum order price to be £10, meaning that the customer has a choice, either buy two items or not bother. Sometimes it can actually cost you money to send out products than just walking away. The minimum order option in the checkout prevents this type of loss.
Control how your customers checkout, only viable sales make it through to sale.