A billing application

The requirement is for a lean billing system at multi sale counters at different locations. The need is to track no. of different items sold at different counters. This might need a product master, customer master, rate master,sales transaction, location master, void transaction and etc. I would like to have the app on a cloud(internet) and in case of internet failure, the system should be able to store information in the local drive and during next connect it should auto sync with the server. The sales report should be customer wise, item wise, day wise, location wise, time wise etc. Please share your thoughts. Thanks, Antony