In normal situations, whoever is logged in at the POS is who ends up as the employee registered to a specific sale. But this can be manually changed afterward if you would like to.
To Update The Employee Attached To A Sale:
Navigate to Reports > Sales Detail Report
Find the sale you would like to edit. You can narrow down your available options by filtering by a date range.
Click the gray edit icon to the right of the sale you wish to fix.
A modal will pop up. Here you can use the cashier dropdown to change the employee attached to that specific sale.
Click Save