Often times you want to log time in 5-minute time increments because it's easier communicate and understand. However, this is tricky. The system needs to convert your time to a rational number and 5 minutes doesn't round to a very clean number. It's a fraction with a repeating decimal (0.083333333) of minutes when applied to an hour (i.e. 60 minutes)
When trying to calculate 5 mins of time, the closest you get is 0.08 if you are only showing rational numbers to the 100th place. This will then convert to 4.8 mins (.08 x 60). The reason we need to convert to a rational number is so that it can be multiplied
This is why the standard has always been to bill mostly in 6-minute increments. This allows you to convert this time into a clean rational number (i.e 0.1) and then multiply this by your rate plan.
For example: You bill 1 hour @ $100. Your rate time would be seen as such.
1hr: 1 = $100
45 mins: 0.75 = $75
30 mins: 0.50 = $50
15 mins: 0.25 = $25
6 mins: 0.1 = $10
However, when trying to calculate 5 mins of time it would equal $8.33 ($100 x 083).
