Hi this is how i think about this problem.
There are 2 possible assumptions. A tie is ratified (1) or a tie is not ratified (2).
Starting with 2 bankers left, (1) 12-0 and (2) 0-12.
3 bankers: (1) 11-0-1, (2) 11-1-0. The banker receiving 1 will accept because when he doesnt he will receive nothing.
4 bankers: (1) 11-0-1-0, (2) 11-0-0-1
5 bankers: (1) 10-0-1-0-1, (2) 10-0-1-1-0