can't make border-radius on dt

I cant make border-radius on my dt? Why http://thistedbolig.konggulerodhosting.dk/ What to do? i really need to make the border-radius?? I have tried many things, but none of them works. So i hope one here can help me to be done with the project.

.dropdown dt { border-radius: 10px 0px 0px 10px;}



        <div class="small-6 medium-3 columns">
          <dl class="dropdown">

            <dt>
            <a href="#0">
              <span title="city" class="hida " ><img src="assets/images/search/placeholder.svg" alt="" style="width:20px; height:20px; margin-right:10px;">Vælg en by</span>
              <p class="multiSel"></p>
            </a>
            </dt>

            <dd>
                <div class="mutliSelect">
                    <ul>
                        <li>
                            <input type="checkbox" value="Thisted" />Thisted</li>
                        <li>
                            <input type="checkbox" value="Snested" />Snested</li>
                        <li>
                            <input type="checkbox" value="Vesløs" />Vesløs</li>
                        <li>
                            <input type="checkbox" value="Nors" />Nors</li>
                        <li>
                            <input type="checkbox" value="Sennels" />Sennels</li>
                        <li>
                            <input type="checkbox" value="Østerild" />Østerild</li>
                    </ul>
                </div>
            </dd>
        </dl>
        </div>