[iOS]保留两位小数

1. 四舍五入

CGFloat rounded_up = round(0.355 * 100) / 100;
NSLog(@"%.2lf",rounded_up);

2. 直接进1(天花板函数)

CGFloat rounded_up1 = ceilf(0.355 * 100) / 100;
NSLog(@"%.2lf",rounded_up1);

3. 舍弃后面所有位数(地板函数)

CGFloat rounded_up2 = floor(0.355 * 100) / 100;
NSLog(@"%.2lf",rounded_up2);