I have searched for similar questions related to border-radius in IE 11, but only one found on the Microsoft IE Developer site described what I am also currently experiencin
I think you are forgot anchor tag reset property in your css.
Actually IE Automatically taken 1px Border, You Must write reset property in your css img tag, a tag border:none
Like Below Code
img {border:none;outline:none} a {border:none;outline:none}