<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
</style>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script>
$(function() {
alert($('[data-role="carttotal"] span').text());
});
</script>
</head>
<body>
<div data-role="cartbonus" style="text-align: left;">Бонус: <span>50 руб</span></div>
<div data-role="carttotal" style="text-align: left;">Итого: <span>750 руб</span></div>
</body>
</html>