What files should I be attaching to my application if they don't specify?

I did a search for this but couldn't really find any good answers.

So I've been applying to jobs seriously for about a month now and have had a few applications where it basically just says "add supporting documents here" and doesn't say which ones they want. The one I'm looking at right now, for instance, says "You can attach files to the candidate record (e.g.: cover letter, resume, references, transcripts, etc.)." and just has the file upload section below with no guidance.

This particular application, in the job description part, said that they needed a transcript so I included that. But usually what I send is just the cover letter, and a letter of recommendation I got when I finished my internship. Should I be attaching my references, too? I have been inputting them when asked, but otherwise have just been saving them for the interview. And my GPA was 3.085, so while not embarrassing it's not really worth bragging about either - but should I be attaching my transcript (I definitely will for this one, but in the future)?

Thanks!

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