Both meanings are common. To me, those two meanings are actually closely related.
ざっくり or ザクッ is primarily an onomatopoeia for the coarse "friction" noise produced when you deeply cut fiber-rich objects (cabbages, pumpkins, thick cloths, etc), trample snow/gravel, or dig in the soil with a shovel. You can hear typical ざっくり sounds in this video. (By the way, how do you describe this sound in English? I'm not sure, but maybe "zap" or "crack"?) We also say ざくざく when such a noise is made in rapid succession.
So the ざく sound is basically a fairly rough noise. By extension, ざく/ざっくり(と)/ざくっと by itself started to gain the sense of roughness/coarseness.
- ざく切りにする to cut something into chunks (in cooking)
- ざっくりと編んだセーター roughly knitted sweater
- ざっくりとした説明 a rough explanation
- ざっくり10万円 roughly 100 thousand yen
If I remember correctly, this usage was a little humorous and slangy in several decades ago, but now it has become commonplace.