How to round off times (DayJs) by 1 minute, 5 minute, 15 minutes, 30 minutes, etc

I'm working with time in React Native using DayJs. When picking 2 different points in time to get the difference between the two, the code seems to be slightly inconsistent.

Most of the time it works well e.g. 10:00 and 18:00 - 45 min. break = 7.25 hours. But once in a while it gives 7.233333... because the points in time picked are 2023-07-04T08:00:58.183Z and 2023-07-04T16:00:05.200Z which indeed converts to that amount.

Is there a way for me to round off these times by (in my case) 5 minutes?

Extra info:

• I'm using import DateTimePicker from '@react-native-community/datetimepicker'; for my timepicker

timeFormat="HH:mm:ss.SSS"

const roundToNearest5Minutes = (time) => {
    const roundedMinute = Math.round(time.minute() / 5) * 5;
    return time.startOf("minute").add(roundedMinute, "minute");
};
const calculateTimeDifference = (startTime, endTime) => {
    if (startTime && endTime) {
      const roundedStartTime = roundToNearest5Minutes(dayjs(startTime));
      const roundedEndTime = roundToNearest5Minutes(dayjs(endTime));
      const diffInSeconds = roundedEndTime.diff(
        roundedStartTime,
        "second",
        true
      );
      const diffInHours = diffInSeconds / 3600;
      setTimeDifference(diffInHours.toFixed(2));
    }
};