Selling in HALF increments only

[aboveallfabric]

Okay - so I would like to be able to sell half units - and multiples of 1/2. (.5, 1, 1.5)

I set my decimal to one.

I set my min amount to .5

I set my product units to .5

Everything seemed to being great....until I got an order from a customer for .6

How can I restrict it to only allow half increments? I really have no desire to do attributes.

Thanks for any insight.

Melanie

[aboveallfabric]

Man - I am really hoping someone can help me figure out what to do! Please