A simple mixin that takes a target size and adds a min-width media query and a IE fallback given by a variable for the content.

_respond-to-ie.scss

@mixin respond-to-ie($size){
  @if $old-ie {
    @content;
  } @else {
    @media all and (min-width: $size) {
      @content;
    }
  }
}

Usage

First you have to declare some variables. They might look like this:

$breakTiny: 320px;
$breakSmall: 480px;
$breakMedium: 768px;
$breakLarge: 960px;

Main file styles.scss

Than after importing the mixin to your scss file, you can use it like in this example:

$old-ie: false !default;
@import "respond-to-ie";

@include respond-to-ie($breakMedium){
    body {
        margin: 0;
    }
}

This will produce the following CSS code in your styles.css file:

@media only screen and (min-width: 768px) {
    body {
        margin: 0;
    }
}

Secondary file for old IE old_ie.scss

$old-ie: true;
@import styles.scss

This will create a second file old_ie.css with the following content:

body {
    margin: 0;
}

So it's basically the same content but without the media query.

Including the files into your HTML

You simply a conditional comment to include those two files and every browser get's only one of the files with only those properties, that the browser supports:

<!--[if lte IE 8]>
    <link rel="stylesheet" href="old_ie.css" media="all" />
<![endif]-->
<!--[if gt IE 8]><!-->
    <link rel="stylesheet" href="styles.css" media="all" />
<!--<![endif]-->