I tried to make this comment a reply to a separate comment but it errored out. I had a funny thing happen to me in college that ruined my one chance at a 4.0 semester. I had just begun my physics major but had some electives to take as well.
I was taking the introductory microeconomics course. At the end of the semester I had received a B and I was relatively certain that I had achieved better, so I went to the professor's office and asked to see how my grade had been calculated. As he started showing me the scores, I realized that none of them had been mine! In the end he had mixed my scores with another student who had the same last name (a very common name, in the professor's defense). I was very happy at that point because I was really thinking I would receive an A! Sadly, the professor shook his head and said that I would still only get a B.
I was a bit shocked so I asked what the final calculation had given and he said a 0.8994. There were not 10,000 points possible and final grades had to be a two-digit representation of the semester's work, so I was unsure why this kept me from an A. I explained to him that the last digit was not significant since there was no "point" to represent the digit, basically trying to explain significant figures to him. I then stated that since the grade had to be either an 89% or a 90%, surely it was more appropriate to receive a 90%.
He shook his head again and said to me what was probably one of the most infuriating and condescending things I'd ever heard from a moron with PhD. He said that economics as a field was likely much more difficult than my primary coursework and that I should not take it too hard that his course was my lowest grade that semester. Now I do not really buy into the perceived/nearly mythical reputation of difficulty that physics has gained, but I do know that we at least put our dependent variable on the appropriate axis. I am not an exceptionally gifted student, so I never did have another chance to receive a 4.0 semester in my math and physics coursework. I have always held a grudge against that professor.
EDIT: I realize I forgot to mention the part that was really infuriating, as I see that it is really not that frustrating as told. The thing that angered me the most, and the reason I went on about significant figures, is that the professor himself was not against rounding! He said that had I received an 0.8995 I would get the A! His entire grading framework was hinged on a poor understanding of math.