* ENH: Use regular rounding to calculate order amounts.
We previously tried to prevent accidental over-ordering by truncating
orders down unless they were within 1e-4 of the next higher integer.
Unfortunately, this makes it easy for a sell order to be one share short
of the desired position.
Using regular rounding treats both buys and sells in the same way.
* ENH keep non-rounding behavior consistent, but leave code structured to make easier to override
* DOC make round_order public and describe behavior in docstring