Magic v magic realism in The Round House and eleswhere

Does magic have any place in a crime novel? I don't think so, which in a way means that if there's magic in the web of it, it's not a crime novel. I've been dancing around the parameters of genre definition with Louise Erdrich's The Round House and, as noted in earlier post, have come to accept that it's a novel about a crime but not a crime novel; if I had any doubt, I'm pushed to certainty by the narrrator, Joe's, discovery in the lakebed of a submerged plastic doll; he hauls it up and it's filled with about $40,000 in hundreds. He and an older woman, married to his uncle (?), whom he's got a huge boyish crush on, deposit the $ in various bank accounts and then bury the checkbooks - his stash for college. Very noble, but is this plausible? I can't accept that he would find the money in such an improbable manner, and that this money will be a significant clue in determining who assaulted his mother. It's a novelist's convenience, not a narrative likelihood - and yet - Erdrich tills the ground for this unlikely discovery by having Joe suspect that his magical totem led him to the doll. So what's really happening is we're verging on magic realism, a very worthy genre - but let's not lose site of the "realism" component. Magic realism at its best works when a novel is so profoundly credible that we almost unknowingly accept certain magical or supernatural elements: it's important that these are elements and not drivers of the plot; e.g., within the carefully delineated world of 100 Years of Solitude, in which the narrator tells is all events of the town over a century in near-obsessive detail, we can accept for ex. that one character is always bedecked with clouds of butterflies. We can accept a single instance of death by spontaneous combustion in Dickens. But in a more loosely narrated - first-person narrated - story like The Round House, an authorial resort to magic to move the plot in the direction she wants just brings me up short. I feel differently about the ghost that appears earlier in the novel; that seems to be a tribute to the thoughts and legends of the Dakota Indians - it's an image, a mystery  - but the events of the novel do not (at least yet) hinge on what the ghost does or says or doesn't say. Magic in a novel can be an opt-out; magic realism can be a way to enhance the reality of the novelist's vision.