How much do grades REALLY matter for residency?

it's my first semester of school, and my school grades with Z scores. it's pretty much impossible to get an A in a class unless you get high 90's across the board on every test, which isn't happening for me. I'm pretty sure I'm getting straight B's, maybe one C and one A this semester and was wondering how much residencies weigh grades? thank you
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums