65
Take the minute value, divide by 5 rounding up to get the next highest 5 minute unit, multiply to 5 to get that back into in minutes, and construct a new NSDate.
NSDateComponents *time = [[NSCalendar currentCalendar]
components:NSHourCalendarUnit | NSMinuteCalendarUnit
fromDate:curDate];
NSInteger minutes = [time minute];
float minuteUnit = ceil((float) minutes / 5.0);
minutes = minuteUnit * 5.0;
[time setMinute: minutes];
curDate = [[NSCalendar currentCalendar] dateFromComponents:time];