how to make moving spinner's edges rounded css

Question

Here is my fiddle link. I created a moving spinner with css. But black part which is spinning/moving should have rounded edges. Can't get it from what I have now.

.loader {
    position: relative;
    border-top: 10px solid #805da4;
    border-right: 10px solid #805da4;
    border-bottom: 10px solid #805da4;
    border-left: 10px solid #000;
    -webkit-transform: translateZ(0);
    -ms-transform: translateZ(0);
    transform: translateZ(0);
    -webkit-animation-name: spinner;
    -webkit-animation-duration: 3s;
    -webkit-animation-iteration-count: infinite;
    -webkit-animation-timing-function: linear;
    -webkit-animation-delay: 0s;
    display: block;
    border-radius: 50%;
    width: 100%;
    height: 100%;
}

Answer 1

in HTML code

<div class="highlightRoundBox">
<span class="loading">
<span class="edge edge-left"></span>
<span class="edge edge-right"></span>
</span>
</div>

in CSS code

@keyframes spin {
    0% {
        transform: rotate(0deg);
    }
    100% {
        transform: rotate(360deg);
    }
}
.highlightRoundBox {
    position: relative;
    margin: 11px 27px 13px 6px;
    width:68px;
    height: 68px;
}
.loading {
  display:block;
  position:relative;
    border-radius: 50%;
    width: 100%;
    height: 100%;
    border: 0.5rem solid #805da4;
    border-top-color: #000;
    animation: spin 1s infinite linear;
}
.loading .edge {
  display:block;
  position: absolute;
  border-radius: 50%;
  width: 0.5rem;
  height: 0.5rem;
  background:#000;
}
.loading .edge.edge-left
{
   top:0.22rem;
  left:0.2rem;
}
.loading .edge.edge-right
{
  top:0.20em;
  right:0.22em;
}

check link https://jsfiddle.net/4yL3rp38/22/