Obviously decimals are simply six minute increments. It isn't too difficult to round the time up or down to the nearest six minutes without ever being more than 3 minutes adrift. This can be further honed by adjusting the time of start and finish to refine the total "error" to a minute or two per sector in most cases. Similarly, if one sector has you gaining a minute or two, the next sector likely can be adjusted downwards to keep the margin of specific error in check.