Standard Pack Preference

We would like to set up a preference for some items to require customers to order in standard pack quantities.  On some items, we package them in bags of 100 but price them by EA.  We want orders to be entered in quantities of 100 only.

We tried setting up advanced preferences using RNDSTDPK - Round to Standard Pack.  When we set it up in PY, it allowed us to enter any quantity on the order.  When I read the description of the preference, it appears that the preference is for demand planning but I was hoping that it would work for order management.