Auto generate pixel fallback when using root-ems

use-rems.scss

@mixin use-rems($property, $size1, $size2:null, $size3:null, $size4:null) {
  @if ($size4) {
    #{$property}: $size1+px $size2+px $size3+px $size4+px;
    #{$property}: ($size1/10)+rem ($size2/10)+rem ($size3/10)+rem ($size4/10)+rem;
  } @else if ($size3) {
    #{$property}: $size1+px $size2+px $size3+px;
    #{$property}: ($size1/10)+rem ($size2/10)+rem ($size3/10)+rem;
  } @else if ($size2) {
    #{$property}: $size1+px $size2+px;
    #{$property}: ($size1/10)+rem ($size2/10)+rem;
  } @else {
    #{$property}: $size1+px;
    #{$property}: ($size1/10)+rem;
  }
}

Requires sass 3.2

Also assumes that you are setting your base size to 62.5%