Advanced POS Customization

I need to customize a web-based advanced POS system with the following features:

- Online and offline data shrink for:
- Sales data
- Inventory data
- User activity logs

- Add dual currency billing: USD and Congolese Franc

Ideal Skills & Experience:
- Strong background in POS systems
- Experience with web-based applications
- Proficiency in handling dual currency integrations
- Ability to manage data synchronization for online/offline access

Please provide relevant work samples and a brief proposal.