Edit in JSFiddle

@mixin border-radius($radius) {  
  -webkit-border-radius: $radius;  
     -moz-border-radius: $radius;  
      -ms-border-radius: $radius;  
          border-radius: $radius;  
}  
.container { 
  @include border-radius(20px); 
  background:yellow;
  text-align:center;
  padding:20px;
}  
<div class="container">
 This is SCSS Mixin
</div>