There are 3 things you can do when you win small sums:
1. Let the small amounts stay in your account until the next time you want to play.
2. Play some more lotto and increase you chances of winning
3. Donate the amount to the Red Cross.
The choice is up to you. Personally, I usually play some more lotto so that I have a greater chance of winning the jackpot, while at the same time knowing that 40% of my money goes to charity.