if he initially has no money and sells the tickets strictly in the order people follow in the line?

I realized after many attempts that the key to everything is to keep track of the nr of banknotes and not the change available.

Anyway, these should be useful tests to run your sw against:

tickets([25,50,50]) > 'NO'
tickets([25,50,25,50]) > 'YES'
tickets([25,25,25,25,50,100,50]) > 'YES'