Ithink this is a multi-faceted question. It really depends on the hunting situation. In all situations, you have to maintain safety, beyond all else. PERIOD.
The deer gun hunting that I do in Ontario, is much different than what I perceive that an BC hunter would do. Typically, my shot are 50 yards or less, with only a few seconds to make up your mind whether you should take the shot or not. Safety being the key factor. PERIOD. If I have good situational awareness, and know where my fellow hunters are, and a Deer comes within my zone of fire, and I don't see any Orange, the deer is getting shot at. Front, Side, Rear, Quartering presentations. If I feel the deer is moving to fast, is to far away or for whatever reason, I don't feel good about it, I will NOT take the shot. PERIOD.
All this happens, extremely fast, in the thick brush of Ontario hunting.
On the other hand, when I am Bow Hunting for deer, the target must not be moving, it must be calm, ie. it doesn't know I am there, and it also must be broadside, or quartering away, and it must be within 20 yards. Those are the limits I place on myself for bow hunting.
From what I gather, a lot of this does not come into play in the western provinces, because you typically hunt in more wide open areas, and do more of a stalk on deer, and typically have up to minutes to decide when to take a shot, not seconds, like is typically found here. My opinions might be completely wrong, and feel free to correct me if I am. And oh yeah, to the question of the amount of rounds I take, I take 40 rounds for our deer hunt, I have never used more than 4, 2 times, two deer had two rounds each into them, the rest I only had enough time for one shot before the deer disappeared. I have lost a couple, not due to not trying to find them, but the vast majority, 90%, are recovered.
So I would say, that I have to be a least 50% sure of my shot connecting while gun hunting, and 99.99% sure when bow hunting. Duck and geese, well, that's a whole another discussion.