Fair enough, this is mostly what i do but since the runtime has been forgiving, i'll need to triple check that. I label all pure money fields as decimal, but am less confident for the ProductQuantity kind of fields. I typically use int for whole numbers but wouldn't be surprised if i used float occasionnally for quantities accepting decimals.
In cases where you have to convert from float/double to decimal you should use an explicit rounding method, not just a raw cast.