This example by Vitalik Buterin is from 2014, but he does show an implementation of a generic quicksort algorithm that can sort object pairs. Now, I'm not sure of the "gas constraints" involved, but with a sorted object pair it should be relatively straightforward to sort by "limit price", "database ID".

For added utility, we will make our sorting function generic: we will sort pairs instead of integers. Thus, for examples, [30, 1, 90, 2, 70, 3, 50, 4] would become [ 30, 1, 50, 4, 70, 3, 90, 2 ]. Using this function, one can sort a list containing any kind of object simply by making an array of pairs where the first number is the key to sort by and the second number is a pointer to the object in parent memory or storage.

Link: Advanced Contract Programming Example: SchellingCoin
Link: GitHub SchellingCoin implementation from Ethereum Repo

I admit I'm not well-versed in EC20 contracts or serpent/solidity, but technically, shouldn't we also be able to see all the current bidders and make an outside calculation of what the expected price would be before the window closes? If so, even better if someone could "cancel their order" before the window closes if they are displeased with the expected closing price.