When planning attacks do you round up or down the number of hits you will get as the attacker and the number of hits the defender will get?
To keep it simple in my head, I round my attacks down and the defenders up. If I am likely to win that way, then I will do the attack if it is minor.
Simply put, attacking 5 armor is 2 hits, defending it would be 3. So I would not attack 5 armor with 5 armor as it is a coin toss and to be safe I favor the worst case to keep me from making rash attacks.
So what do you do when planning in your head?
Round them as you stated and assume that any BB/CA amphibious bombardment will miss (and enemy ones will hit) and at least 1 AA hit, depending on the number of planes.