CiviDiscount - applying sales tax on discounted price rather than original price
We've patched Cividiscount extension which now ensures that the discount also gets applied to VAT/Sales Tax when it's applied to price options.
Here is the PR link: https://github.com/dlobo/org.civicrm.module.cividiscount/pull/131

Have also updated the ticket: https://issues.civicrm.org/jira/browse/CRM-16861

Thanks