Its because of the rounding. Calc 1 in your example is actually 1.10471... Since you are asking it to equal 1.105 it is skipping the first line, and the second is true.
Make your first line IF round([Calculation1],3) = 1.105 THEN "A"
and it works.
Now that you mention it I feel a bit silly. But I'm glad I know.
It will not happen to me again.
In all fairness, I had never ran across having to round in a calculation. I'm glad you had the question, or I would have been posting asking the same thing some day probably very soon! Have a good one.