The number 7.68 is between 7.5 and 8. Let's find which of those two numbers 7.68 is closer to. We can do this by subtracting 7.68 from each of those numbers:
8 - 7.68 = 0.32
7.5 - 7.68 = -0.18
7.68 is 0.32 away from 8, but it's only 0.18 away from 7.5. So, the nearest half is 7.5.
