This plugin is easy to install and execute. It's also very affordable.

POS in my country costs anywhere from $99 to $300 per month, depending on the complexity of automation, integration and features.

Vitepos unlocks this for slightly more than $100 per code.

The UI is clean and functional. You can configure most stuff without the need for a knowledge base or tutorial.

Your customer will have a separate login page from your main wordpress site after you complete the configuration. They will never guess that the backend is wordpress. Haha!

If you're looking for an affordable POS to play with, look no further.