Does the talk count as invited if my PI invited me? I'm a just-graduated undergraduate in Biology/Bioinformatics.

In a month or so, I'll get to give a short (10-minute) talk at a major conference during one of a handful (5?) 50-minute workshops (I'm so excited!).

The other 4 speakers were invited to talk by my principal investigator. He also invited me to give a talk. My PI applied to give the workshop—it’s a competitive proposal-based thing, I think. 

I'll be applying to graduate school in a couple of months and plan to list the talk on my CV.

I guess it's officially an invited talk (by the criteria here and here, at least), but that feels somewhat contrived since it's my PI who invited me. 

Should I go ahead and list it as an "invited talk" on my CV, or would "contributing talk" be more honest?

Thanks!
Since you have graduated already I would say that it is perfectly fine to list it as "invited". If the other speakers are able to do so, then you should also. This is especially the case since your use of the CV is for graduate school admission, not some later career stage purpose. 

It might be a bit presumptuous to list a ten minute talk as an invited talk if you had just earned a doctorate with this professor, but for someone in your position it is an honor to be asked, even for such a short talk. I'll guess that few such BA/BS students are in a similar position. 

However, while the "invited" part seems fine to me, you might want to take care about how you state the rest of the description. "Invited talk" might imply more than you intend. "Invited short talk" or "Invited workshop presentation" might be more accurate. I assume you don't have a lot of these requiring a general description for a section of your CV. 

Your advisor had options about who to invite. He wasn't obligated to invite you and trusts that you have something to offer. 

However, since he will be writing you letters of recommendation for grad school, I assume, you can ask him what is best here.