Tracking daily cash and Pix receipts is still chaos for small business owners

My dad runs a small gas delivery business and logs every Pix and cash payment in WhatsApp messages to himself throughout the day. At the end of the month, there's no total — just a wall of messages he has to scroll through and add up by hand. He loses 30 to 60 minutes a day on this. He can't use a regular spreadsheet because employees move around the shop and he doesn't want them seeing the numbers, so whatever solves this needs a password on the home screen. I've looked and everything in this space is either heavy accounting software built for accountants, or generic finance apps that don't fit how a small business owner actually works. This would have to be in Portuguese — the market is small Brazilian business owners (gas, water, small commerce) who'd never use anything in English.