Our current POS system allows the cashier to enter the count of each denomination in the cash register, and the system computes the total. Please see the attached screenshot. This is a useful feature for the cashier, especially at the end of a long day, and when there are several rolls of coins in the Cash Register.
Are there any plans for adding this functionality to Square for Retail? If not, we can develop an app in-house. Does Square Register allow the user to install custom apps?
We’re constantly working to improve our features based on feedback like this, so I’ll be sure to share your request to the API product team. Unfortunately at this time the ability to load additional apps on the Square Terminal isn’t currently available. 
Thank you for your prompt response.
My apologies, in that I wanted to know whether we can load custom apps on the Square Register and not on the Square Terminal.
I have edited my original post.
At this time the same applies for Square Register. Additional apps can’t be loaded on the device.
Thank you for your prompt response.