What is the proper workflow for slightly different framerates, i.e. 30, 29.97, 29.976?
First off, you are correct in your assumption that 23.98 and 24 are indeed different. They are not effectively the same, and they are not "rounded up". Sometimes 24p means 23.98, and sometimes it means 24. They are both separate and it can be quite problematic to treat them the same.

But in practicality, you don't need to worry about the quality, especially if you are using something like Premiere, which is very good about matching your sequence settings with those of your footage (and warning you if they aren't the same).

Your 60D does indeed shoot in 23.98, and modern editing software will know the difference. You can make a 23.98 sequence yourself if you wish; your footage will suffer no quality loss, as no conversion is actually occurring.

Thankfully, the reason we have to distinguish between 23.98 and 24 is that we are moving on from the standards and hurdles that lead to drop-frame frame rates. Plenty of new cameras (such as the RED) can shoot 24fps, and they actually mean 24. And doing exactly that can be quite nice.

So yeah, don't worry about it. Just always match settings with your footage, but newer versions of Premiere do this without fail, faster and accurately.