You don't need a cash register to print a receipt. A simple thermal printer will do. For printing from a phone, it is more convenient to connect via bluetooth.

It is impossible to print a high-quality picture of a receipt available by reference on a thermal printer due to the limitations of thermal printing technology
The application receives information from the tax service api and generates a print job for the printer driver using text print commands, etc. This makes it possible to achieve the clarity and readability of the receipt laid down by the printer manufacturer.

The application requires the installation of a special driver from Goole Play.