Unit of Measure when less than a unit

I have a unit if measure problem.  For example, a unit of ours can have 12 bottles in a box.  1 Unit = 12 Bottles.  So, I have a unit of measure schedule of an inner (or bottle) to be 1/12th of a unit or a Bottle = .08333, fully using the 5 decimals places available.  We have large customers that only order by the bottle, via EDI that I can't change.

So, when they order 12 bottles it does not equal 1 unit.  It equals .99996 ... which should be 1 unit.  This is causing problems when picking the order(s).  Anybody know how to get around this kind of issue?