Time rounding is the time unit used by the supplier to round up your talk time. If you look at your residential phone bill, you will find all end up to minutes. This is caused by rounding.

Usually, rounding is in one minute, i.e. if you talk for 23 min and 27 second, it will count as 24 minutes.
For Example: A 3 minutes rounding card means if you call 1 minute and 20 seconds, it will count 3 minutes. So, you will save money if your call time is a multiple of 3.

As you can see this card is suitable for heavy users 'cause It will not make big differences if you talk more than 20 minutes. But if you talk less than 5 minutes, we suggest you to use cards that is one minute rounding.

Here is what you can do. Ask your card's rounding, use a stop watch to count your time. if it is one minute rounding, don't go over 50 seconds after integer minutes.