:target::before {
  content: "";
  display: block;
  height: 60px; /* fixed header height*/
  margin: -60px 0 0; /* negative fixed header height */
}
Or:
html {
  scroll-padding-top: 70px; /* height of sticky header */
}

Or use jquery:
var offset = $(':target').offset();
var scrollto = offset.top - 60; // minus fixed header height
$('html, body').animate({scrollTop:scrollto}, 0);