App that assist distributing a pot

So I am managing a restaurant where tips are distributed partly according to staff seniority and also whether they are waitering or kitchen staff (chef do not get tips but kitchen assistant do, but a smaller slice compared to waiters).

Additionally, there are days where waiters have day off, so their share will naturally be redistributed amongst the rest.

I was wondering if there is an app that allows one to easily work out the distribution according to percentage set by the owner, while easily toggle staff on duty on and off (so as to auto redistribute things). One final requirement is that it would be nice if you can set the minimum denomination (e.g. 0.5, whole number, 50 or whatnot.. not xx.666667 etc.).

Perhaps too specific, but I suppose that something text box that allows you to enter the total in the pot, add entries with a percentage, and a slider to make adjustment will do.

Spreadsheet? Might need a few conditional statements to allow for who is on shift, but it depends on how tips are divided up, ie is it done per shift, per day, per week or on a monthly basis.

I'd suggest looking into how pirates divided up their treasure.
Basically each person got a number of shares, based on their rank. In your case you'd total the day's tips, divide it by the number of shares present on that day (those not at work obviously get no shares) and then multiply it back up by the share number each individual gets... which will tell you how much to pay each person.

Alternatively, these is the old Royal Navy rules (pre 1808) for splitting prize money:

1/8th for the Flag Officer (or Captain if sailing under Admiralty orders)
1/4th for the Captain(s)
1/8th for the Lieutenants, Surgeon(s), Master(s) and RM Captains
1/8th for the Wardroom ranked Warrant Officers, RM Lieutenants, Chaplains, Secretary to the Flag Officer
1/8th to the Midshipmen, junior WOs, senior mates and RM Sergeants
1/4th for the remainder

So breaking it something like that gives you what each job role is entitled to from each day's Tip Takings. Then divide that by the number of people doing that job on that day to see what each person gets.
The titles aren't important, only the fractions which must add up to a whole.
You could go further and use 1/16ths or 1/32nds, if you like.

Both of these can be done quite easily in a spreadsheet, which you can also print off and post on the noticeboard so people can see your honesty, as well as saving each sheet for future reference. Add a box that each person signs when they receive their tip payments, if you like.
You could quite easily knock something up that auto-calculates each person's shares of each day's tip pot based on whether they were present or not, totals it for the end of the week/month and only requires you to input the total tips value each day (or even week) and put an X under each name and day(s) they worked.

The only problem you have then is any cash tips handed to people personally, unless you disregard them anyway.