Javascript how to remove decimals after the comma

Question

    function deductibleAmount(FileSize) {
    return FileSize / 1000000 + " MB";

}

So this is the function I have to turn my FileSize in bytes to MB but the outcome looks something like this: 27.254161 MB but I want 27.25 MB therefor the four last decimals will have to be removed. How can i do this?