Indeed honesty is the best policy. I encountered the exact test when I was working in the bank a random customer just work in to my cubicle with a huge sum of cash, the money she intended to pay in was far more below than what she handed over to be, like overreach of 750k was on top. I asked the lady how much she intended to pay in and she told me 350k. So I counted out 350k and handed over the remaining 750k to her, she thank me and left. It was later in the evening that my boss told me that it was a test, and he celebrated me, since then I was the one who used to count his money and he used to give me tips. Lesson is that it always pays to be honest! I wish you success!