Build a Website

I have a simple cart built in html that I need more advanced features added in. Right now it calculates everything using TotalIt: <script> function totalIt() { var input = [login to view URL]("product"); var total = 0; for (var i = 0; i < [login to view URL]; i++) { if (input[i].checked) { total += parseFloat(input[i].value); } } [login to view URL]("total").value = "$" + [login to view URL](2); } </script> I need it to also include estimated taxes. I also need products to have quantity for it instead of just check boxes. The membership quantities need to be discounted. So 1 Membership is $75, two is $120, 3 is $150, and 4 is also $150. Also if you could make it look a lil more professional, that would be awesome. Shouldn't take too long, as I wrote most the html in 30 minutes. So I have one item that is $75 but if they buy two I want it to be $120, 3 will be $150. 4 will also be $150.