The official statement from Google regarding this is that they “generally don’t follow nofollow links”. This means that there are certain special circumstances under which they do follow such links.
However, even when they follow it is mostly for improving their own understanding and internal purposes, not to pass any link juice. So, for all intents and purposes, you can simply assume that nofollow links will not be followed by Google, at least not in a way that directly affects your SEO.