mrmen2,
пройти циклом проверить checked суммировать данные ...
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
</head>
<body>
<input type="checkbox" value="12321" name="vote" test="0.2">
<input type="checkbox" value="12321" name="vote" test="1.2">
<input type="checkbox" value="12321" name="vote" test="3">
<script>
var votes = document.querySelectorAll('[name="vote"]');
function s() {
var sum = [].reduce.call(document.querySelectorAll(":checked"), function(a, b) {
a += +b.getAttribute("test");
return a
}, 0);
alert(sum)
}
for (var i = 0; i < votes.length; i++) votes[i].onchange = s;
</script>
</body>
</html>