Is there a way to add a sales person to a ticket? And also be able to track the salesperson performance for commisions for example.

If I understand clearly, you need to try Employee management addon. It will allow you to create employees and give some rights to them. For example cashier, administrator and so on. And they can do sign in to the POS via personal PIN code and do sales from each personal account. After that, you can view sales analytics by employees in the Back office.

More details:

https://help.loyverse.com/help/how-use-paid-services-loyverse-pos

https://help.loyverse.com/help/employee-loyverses

In our case, we have sales people who talks with the customers and sell products. Also there two people at the cashier who are responsible for only billing and not selling. Sales people do not use the system. So my question is, Is there a way to tag both the sales person and the cashier to a ticket?