JSFiddle - React, Tailwind, and code Playground

HTML

<html>
    <body>
        
        <script>
            function verify(qty){
               return function(event){event.target.value=Math.round(parseInt(event.target.value)/qty)*qty;};
            }
        </script>
    <form>
    <input type='text' onblur="(verify(12))(event)"/>
    <input type='text' onblur="(verify(14))(event)"/>        
    </form>
    </body>
</html>