How to Stop timer when win the game?

Hi all im a newbie of Unity (installed yesterday) and i’ve followed the tutorial “Roll a Ball” and create the minigame, i’ve added a in-game timer with this code. the question is, how i can stop timer when i collect all the pick ups?

using UnityEngine.UI;
using UnityEngine;
using System.Collections;

public class Timer : MonoBehaviour {
	public Text timerText;

	private float currentTime; 

	// Use this for initialization
	void Start () {
		currentTime = 0.0f;
	
	}
	
	// Update is called once per frame
	void Update () {
		currentTime += Time.deltaTime;
		timerText.text = "Time: " + currentTime.ToString ();
	
	}
}

int collectedTotal = 0;
int winTotal = 10;

void update()
{
 void Update () {
    if(collectedTotal < winTotal)
    {
     currentTime += Time.deltaTime;
    }
     timerText.text = "Time: " + currentTime.ToString ();
 
 }
}

something like this, only increments the timer when the collected total is less than the target.