The GRAJ fee is 5% for every participant. GRAJ can set a lower rate for one participant, for example a very large business running all its trade through the protocol, and can never set one above 5%: the database refuses it. Every change is recorded with who made it, when, the old and new rate and the reason, and you are told in words such as “Your GRAJ fee: 5% → 4%”. Your account page shows your rate and its full history. An order keeps the rate it was charged, so a later change never rewrites a past sale.