Enforcing order multiples

Hello:

  What options are there for enforcing order multiples for specific items on an order line?  For example, we have an item that's stocked and costed with a UOM of Each, however the item is also packaged in qtys of 10, so we want the order line qtys to always be in a multiple of 10.  We'd prefer not to convert to another item #wth a different UOM. 

Any ideas?

Thanks!