Question about the relationship between quantum mechanics and Newtonian physics

I'm a layman with no formal science education beyond a physical science class freshman year of college. I know that quantum mechanics is in-deterministic, while Newtonian physics is generally deterministic. I've read that in theory, if you could control all the initial conditions, you could perform a coin toss infinite times and always achieve the same, predictable, deterministic outcome. Whatever you are using to make the hypothetical coin toss is a physical object made of atoms containing electrons. Electrons behave both as particles and waives and are therefore in-deterministic (I might be misunderstanding so please help me out). You can only measure probabilities when it comes to electron behavior. (again, I might be misunderstanding). Why is it then that the in-determinism of the subatomic particles that make up the physical macroscopic objections do not make the outcomes of that physical object's actions indeterminate?