I don't think that there is an exact correlation between a restaurant's sales and its accounting system or an industry standard...

You need to determine the complexity of recording sales, expenses, etc. and base your bookkeeping system around that. You also need to consider, especially with a restaurant, how you will set up controls to safeguard the Company's assets. i.e. cash, inventory. A documented system with proper segregation of duties will help to mitigate the risk of misappropriation.