Turn a super small into 0

As m_tarler has said, ROUND could work. I would probably consider creating an IF formula, prescribing, as precisely as you can or need to, the min and max of your "super small" label. 

But first, before you go monkeying with valid results, even if small and negligible, it would be appropriate to describe a bit more of the context. Depending on that context, even "small numbers" can have serious consequences when ignored, even if only temporarily.