Will I get docked for including a source in my bibliography which I didn't end up using in my actual paper?
Some students actually try to last-minute pad the bibliography that way. If it doesn't look like that (i.e. noticeable many unused references to sources, which you were expected to read&amp;know), you probably will be ok.

In general, it is better practice to include a reference to a source pertaining to the topic of your paper, even if you are not directly quoting from your reference, than to arouse suspicion of concealing to having "used" it. Depending on the context and regulations, you might even be prompted to add references to non-written material (like a conversation) to the bibliography. 

It is even rumored some reviewers expect their recent work to be referenced, no matter if it's of any real use to your work. On a funnier note, some writers try to sneak in a fun reference (use with consideration!, I'm just reporting what I have seen...).