Follow below steps:
1. Create a slicer to select each cashier one at a time.
2. Create a measure to find the order id that contains cashier_id in it by using below code.
contains = IF(CONTAINS(Orders,Orders[Order Id],Orders[Cashier Id]),"Contain","Not Contain")
3. The above code would return contain or not contain for each order when you would select a cashier id.
4. Now put the contains measure in filter ans show only values for "Contain"
Hope this helps you.