There is going to be some aspects of the design that can't be pixel perfect when it comes to a fully responsive site. This is because of the use of % based widt

There is going to be some aspects of the design that can't be pixel perfect when it comes to a fully responsive site. This is because of the use of % based width to make the grid fluid. If you're looking for pixel-perfect versions you're best off working with breakpoints and keeping the design rigid up until each breakpoint. It's more work, but if you really want/need pixel-perfection then it's really the only way to go.