Issue with forming correct relationship between subtype and another table in ERD
I actually think your diagram is good for your rule. The only thing is that with the relationship line connecting "Cash Accountability" and "Cashier", I would remove the circle on the Cashier side, to indicate that a "Cash Accountability" has to have exactly one Cashier.


  So as it is now, the relationship states that a cashier cashes out many times in a day and I want to express that a cashier only cashes out once per day.


The relationship is simply saying that a cashier can cash out more than once (not necessarily more than once per day), which is technically correct.

You could add a unique constraint to the implementation of your data model between "Cash Accountability"'s EmpID and Date fields in order to enforce that a Cashier cannot cash out more than once a day. Here's how this would be done in MySQL: https://stackoverflow.com/questions/635937/how-do-i-specify-unique-constraint-for-multiple-columns-in-mysql

I'm not sure if there's a "correct" way to display this unique constraint in an ER Diagram, but I suppose you could just add a comment.