Make three sheets. The first one is the income list, indicating the date, items sold, purchase price, selling price, and selling unit.

The second one is the cost list, which includes the daily expenses of the store (all contents, store rent, meals, water and electricity==), purchase date, purchase items, and purchase unit.

The third one is the general ledger. The first one is your turnover and profit, and the second one is your cost. Calculate your business situation for the day. After that, make one sheet every day, summarize once a month, once a quarter, and once a year. That's it.