If you did your rounding properly, you cannot be penalized

Exoneration

RULE 

Part 2 - When Boats Meet

Section C - At Marks and Obstructions

Rule 18.5  When a boat is taking mark-room to which she is entitled, she shall be exonerated

1. (a)if, as a result of the other boat failing to give her room, she breaks a rule of Section A, or
   

2. (b)if, by rounding the mark on her proper course, she breaks a rule of Section A or rule 15 or 16.
   

Buoy room rules do not apply at a starting mark surrounded by navigable water or at its anchor line from the time boats are approaching them to start until they have passed them... 

PURPOSE

Protect the rights of the virtuous boat.