Any chance you could post your settings?
It looks possibly that you were using a very shallow depth of field so it is not all in focus. Iwould at least try to get all of the head nice and sharp if you can... Were you using auto or manual focus? Sometimes, you might need to use a off camera flash to give you the extra light so you can get the whole thing nice and sharp and use use a higher f no?
Thing with macro is keep checking your settings, av mode is really handy ISO 400 to start if handheld, tripod, remote release if you have them...
Does this help feel? free to PM me if you want any more advice (not that I am an expert, but I do use the 105!) there are loads of really good books about macro, nip to your local library!
Rob