Generated by SassMeister.com.

SassMeister-input-HTML.html

<ul>
  <li>
    Equal<br/>height<br/>Test
  </li>
  <li>
    Still not so equal
  </li>
  <li>
    Test<br/>Test
  </li>
</ul>

SassMeister-input.scss

// ----
// Sass (v3.4.12)
// Compass (v1.0.3)
// Singularity.gs (v1.5.1)
// Toolkit (v2.7.0)
// ----

/* Imports */
@import "toolkit";
@import "singularitygs";

/* List styling */
@mixin nobullet {
  list-style-type: none;
  list-style-image: none;
}

%list.unstyled {
  display: block;
  margin: 0;
  padding: 0;
}
%list-item.unstyled {
  margin: 0;
  padding: 0;
  display: inline;
  @include nobullet();
  &:before,
  &:after {
    @include nobullet();
    // content: '';
  }
}
ul {
  @extend %list.unstyled;
  li {
    @extend %list-item.unstyled;
    background-color: green;
  }
}

/* Grid definition */
@include add-grid(12);
@include add-gutter(1/3);

/* Height experiments */
ul {
  
}

li {
  display: inline-table;
  
  @include layout($gutter: 0) {
    &:nth-child(n+1) {
      @include grid-span(4, 1);
    }
    &:nth-child(n+2) {
      @include grid-span(4, 5);
    }
    &:nth-child(n+3) {
     @include grid-span(4, 9);
    }
  }
}

SassMeister-output.css

/* Imports */
/* List styling */
ul {
  display: block;
  margin: 0;
  padding: 0;
}

ul li {
  margin: 0;
  padding: 0;
  display: inline;
  list-style-type: none;
  list-style-image: none;
}
ul li:before, ul li:after {
  list-style-type: none;
  list-style-image: none;
}

ul li {
  background-color: green;
}

/* Grid definition */
/* Height experiments */
li {
  display: inline-table;
}
li:nth-child(n+1) {
  width: 33.33333333%;
  float: left;
  margin-right: -100%;
  margin-left: 0;
  clear: none;
}
li:nth-child(n+2) {
  width: 33.33333333%;
  float: left;
  margin-right: -100%;
  margin-left: 33.33333333%;
  clear: none;
}
li:nth-child(n+3) {
  width: 33.33333333%;
  float: right;
  margin-left: 0;
  margin-right: 0;
  clear: none;
}

SassMeister-rendered.html

<ul>
  <li>
    Equal<br/>height<br/>Test
  </li>
  <li>
    Still not so equal
  </li>
  <li>
    Test<br/>Test
  </li>
</ul>