Currently the timer resets after a task is marked as completed. I don't believe this is the intention of the pomodoro technique. Rather I have always used it in such a way that I try to complete one or more tasks in a pomodoro and take a break when the timer goes off. If reset after every task is complete then the timing of the pomodoros and breaks get messed up.
From the cheatsheet... A Pomodoro is indivisible -- If a task takes more than 5–7 Pomodoros, break it down -- If it takes less than one pomodoro, add it up, and combine it with another task -- Once a Pomodoro begins, it has to ring -- The next pomodoro will go better