Its good to see that you have used code tags in your first post
Now, coming to your issue - ArrayIndexOutOfBoundsException - I assume that you know what this exception means and in which scenario it occurs.
I've not debugged your code, but looking at exception stack trace and other things, I could figure out below things:
1) Dimensions of gameBoard are 5x5
2) In method determineWinners, contents of gameBoard is accessed as gameBoard[coinTosses[r]][coinTosses[r]]
3) Values of coinTosses[r] and coinTosses[r] depend on length of coinTosses, which is 10
4) Thus, there is possibility of value of coinTosses[r] and/or coinTosses[r] being greater than or equal to NUMBERPRIZES.
5) And hence, ArrayIndexOutOfBoundsException.
As I've already said, I didn't go through code line by line and I don't have any idea about which game is this and what are the rules. But what I can suggest is : try to have uniform values for lengths of array. Also, I'm not sure why you are accessing locations of gameBoard depending on values of coinTosses.