I'm very new to JavaScript (I come from a Java background) and I am trying to do some financial calculations with small amounts of money.

My original go at this was:

<script type=text/javascript>

    var normBase = ([price]).replace($, );

    var salesBase = ([saleprice]).replace($, );

    var base;

    if (salesBase != 0) {

        base = salesBase;

    } else {

        base = normBase;

    }

    var per5  = (base - (base * 0.05));

    var per7  = (base - (base * 0.07));

    var per10 = (base - (base * 0.10));

    var per15 = (base - (base * 0.15));

    document.write

        (

        '5% Off: $'  + (Math.ceil(per5  * 100) / 100).toFixed(2) + '<br/>' +

        '7% Off: $'  + (Math.ceil(per7  * 100) / 100).toFixed(2) + '<br/>' +

        '10% Off: $' + (Math.ceil(per10 * 100) / 100).toFixed(2) + '<br/>' +

        '15% Off: $' + (Math.ceil(per15 * 100) / 100).toFixed(2) + '<br/>'

    );

</script>

This worked well except it always rounded up (Math.ceil). Math.floor has the same issue, and Math.round is also no good for floats.

In Java, I would have avoided the use of floats completely from the get-go, however in JavaScript there does not seem to be a default inclusion of something comparable.

The problem is, all the libraries mentioned are either broken or for a different purpose. The jsfromhell.com/classes/bignumber library is very close to what I need, however I'm having bizarre issues with its rounding and precision... No matter what I set the Round Type to, it seems to decide on its own. So for example, 3.7107 with precision of 2 and round type of ROUND_HALF_UP somehow winds up as 3.72 when it should be 3.71.

I also tried @JasonSmith BigDecimal library (a machined port from Java's BigDecimal), but it seems to be for node.js which I don't have the option of running.

How can I accomplish this using vanilla JavaScript (and be reliable) or is there a modern (ones mentioned above are all years old now) library that I can use that is maintained and is not broken?