Have you tried this?
CGFloat val = 37.777779;
CGFloat rounded_down = floorf(val * 100) / 100; /* Result: 37.77 */
CGFloat nearest = floorf(val * 100 + 0.5) / 100; /* Result: 37.78 */
CGFloat rounded_up = ceilf(val * 100) / 100; /* Result: 37.78 */
source : Rounding Number to 2 Decimal Places in C
Complementing: You just don't have control about how the computer will store the float value.
So these rounded values may not be EXACTLY the "obvious" decimal values, but they will be very very close, and that's the max guarantee you will have.
You do that in Objective-C exactly the same as you would in C:
double notRounded = ...;
double rounded = round (notRounded * 100.0) / 100.0;
Don't use float - unless you can explain to someone exactly what your specific reasons are to use float over double. float has very limited precision. And using ceil or floor is daft, since there is a perfectly fine standard function named "round".
Neither float nor double can exactly represent most decimal values, like 12.24. Because it has much higher precision, double will let you get much closer to 12.24. Therefore, there is a huge chance that NSLog will display some weird number for (float) 12.24, like 12.23999997394 or whatever, while it may display 12.24 for double.