<?php
$taxonomyName = "service_line_category";
$terms = get_terms($taxonomyName,array('parent' => 0));
foreach($terms as $term) {
    echo '<a href="'.get_term_link($term->slug,$taxonomyName).'">'.$term->name.'</a>';
    $term_children = get_term_children($term->term_id,$taxonomyName);
    echo '<ul>';
    foreach($term_children as $term_child_id) {
        $term_child = get_term_by('id',$term_child_id,$taxonomyName);
        echo '<li><a href="' . get_term_link( $term_child->term_id, $taxonomyName ) . '">' . $term_child->name . '</a></li>';
    }
    echo '</ul>';
}
?>