I first learned of this tea through Beatrix Potter’s Tale of Peter Rabbit, where Peter is given some medicinally at the end. I pronounced it in my head all sorts of ways. Then I saw an animated production of it, narrated by Meryl Streep (not that I knew who she was at the time, but I can remember the sound of the narrator’s voice from the production and match it up now), who pronounced it “KAM-o-myle”.
I pretty much never hear the word “on the street” so that’s it, that’s how I think the word is pronounced.