_border_radius.scss

// (Using compass's border-radius mixin)

.br-2-2-0-0 {
  @include border-radius(2px 2px 0 0);
}

.br-0-0-2-2 {
  @include border-radius(0 0 2px 2px);
}

.br-2-0-0-2 {
  @include border-radius(2px 0 0 2px);
}

.br-0-2-2-0 {
  @include border-radius(0 2px 2px 0);
}

foo.scss

@import "border_radius";

// I find myself doing this to avoid packing my css files with the 5 lines it takes to define a cross-browser border radius

#foo-1 {
  @extend .br-2-2-0-0;
}

#foo-2 {
  @extend .br-2-2-0-0;
}

#foo-3 {
  @extend .br-2-2-0-0;
}

// BUT!

// I would love to be able to do something like this:
#foo {
  @include my-border-radius(2px, 2px, 0, 0);
}
// ... which would define a top level class:
.br-2px-2px-0-0 {
  @include border-radius(2px 2px 0 0);
}
// ... and extend the current selector with that class:
#foo {
  @extend .br-2px-2px-0-0;
}
// ... that way the border-radius/-moz-border-radius/-webkit-border-radius for 2-2-0-0 only appears once in the generated css.

zbar.scss

@import "border_radius";

#bar-1 {
  @extend .br-2-0-0-2;
}

#bar-2 {
  @extend .br-2-0-0-2;
}

#bar-3 {
  @extend .br-2-0-0-2;
}