Guest check presenters, also known as restaurant check holders, are the common names for the little white device you are describing. It's a handheld calculator-like device used to total bills and give change at restaurants. Common features of these devices include a calculator and receipt printer, as well as a notepad for jotting down details like the table number or a special request. The use of these devices is widespread in eating establishments because they facilitate the viewing and payment of bills in an orderly fashion for customers and allow proprietors to monitor their cash flow.
