gistfile1.css

@mixin border-radius($radius, $prefixes: -moz -webkit -o) {
	@each $prefix in $prefixes {
		#{$prefix}-border-radius:$radius;
	}
	
	border-radius:$radius;
}

#id {
	@include border-radius(5px, -moz -webkit);
}


// Gives you

#id { 
	-moz-border-radius: 5px; 
	-webkit-border-radius: 5px; 
	border-radius: 5px; 
}


// Or make it even more generic

@mixin prefix($property, $value, $prefixes) {
	@each $prefix in $prefixes {
		#{$prefix}-#{$property}:$value;
	}
	#{$property}:$value;
}

@mixin border-radius($radius, $prefixes: -moz -webkit -o) {
	@include prefix(border-radius,$radius,$prefixes);
}