Four ways to divide a cost, when each is the right one, and what to do about the penny that will not divide.
The default, and right most of the time. Everyone in the split pays the same. Use it unless there is a reason not to — a rule nobody has to remember is worth more than a fairer one nobody applies consistently.
Whole units, for when the difference is countable: a couple in one room counts as two, the big bedroom counts as three of five. Easier to agree than percentages because nobody has to do arithmetic to check it.
For a bill where the items are already known — one person had the lobster. Type what each person owes; the total has to match the bill, and you are told immediately if it does not.
For standing arrangements — a 60/40 on the utilities. It has to come to 100%, and it will tell you what it currently comes to while you are still editing.
£10 between three is not a number. Somebody gets 3.34 and the others get 3.33, and every app has to choose. Tabrillo shows you who took the extra penny on the receipt, so it is a fact rather than a discrepancy somebody finds later.
Pay each other however you already do, then record it. Tabrillo can reduce a tangle of mutual debts to the fewest payments that clear it, or leave the pairs alone if you would rather settle directly with the person you owe.