Optimal strategy for online skill game Catch-21

On a famous skill-gaming website there is a game called Catch-21 that is a combination of solitaire and blackjack. The goal of the game is to go through a deck of cards and make as many points as possible. At first the deck is shuffled and you get to either place the first card of the deck into one of 4 piles or to place it in a discard pile. You cannot make a pile go over 21 and if your card would make one of the piles go over 21 you can double click on the pile to discard the last card you put in it. When a pile reaches 5 cards or a score of 21, it is cleared and you get points. When you get a Jack of Clubs or a Jack of Spades you can place it on a pile to automatically clear it and get 75 points. Getting 21 gets you 50 points and getting a 5 cards Charlie (5 cards adding up to 21 or less) gets you 100 points. The game is timed and a large part of your score depends on the time you take to go through the whole deck. What would be the best strategy to play this, and would there be any good way to count the cards? Since you only get points by getting to 21 it would usually be a bad thing to get scores like 9 or 10 since they are unlikely to get to 21, but scores under that are good since they have good odds of making a 5 cards Charlie.