I assume you mean measure the battery voltage every 5 minutes. This thread: http://origin-www.cypress.com/forum/psoc-4-ble/coin-cell-battery-voltage-measurement has examples for measuring battery voltage.
Otherwise, there are a few other battery measurement methods that work in different ways.
If you merely want the battery level to mimic a timer that decrements the battery level by 1% every 5 minutes, then you can use a timer for 5 minutes and an integer that decrements when the timer hits each 5 minutes period. (no examples for this)