Попробуйте это ..
-(NSString*)floatToString:(float)val
{
NSString *result;
NSArray *numbers = [[NSArray alloc]initWithObjects:[NSString stringWithFormat:@"%f",val], nil];
NSLog(@"%@",numbers);
NSArray * floatingPoint = [[numbers objectAtIndex:0] componentsSeparatedByString:@"."];
NSString * lastObject = [[floatingPoint lastObject] stringByReplacingOccurrencesOfString:@"0" withString:@""];
if ([lastObject length] < 2) {
result = [NSString stringWithFormat:@"$ %.2f",[[numbers objectAtIndex:0] floatValue]];
} else {
result = [NSString stringWithFormat:@"$ %g",[[numbers objectAtIndex:0] floatValue]];
}
return result;
}