only round jumbotron corners at 768px+

docs/assets/css/bootstrap.css

@@ -4423,7 +4423,6 @@ a.counter:hover {
   line-height: 30px;
   color: inherit;
   background-color: #eeeeee;
-  border-radius: 6px;
 }
 
 .jumbotron h1 {
@@ -4438,6 +4437,7 @@ a.counter:hover {
 @media screen and (min-width: 768px) {
   .jumbotron {
     padding: 50px 60px;
+    border-radius: 6px;
   }
   .jumbotron h1 {
     font-size: 60px;

less/jumbotron.less

@@ -11,7 +11,6 @@
   line-height: @line-height-base * 1.5;
   color: @jumbotron-lead-color;
   background-color: @jumbotron-background;
-  border-radius: 6px;
   h1 {
     line-height: 1;
     color: @jumbotron-heading-color;
@@ -24,6 +23,7 @@
 @media screen and (min-width: 768px) {
   .jumbotron {
     padding: 50px 60px;
+    border-radius: 6px; // Only round corners at higher resolutions
 
     h1 {
       font-size: 60px;