Taxed Contribution amount is not rounded for processing, causes PayPal WPS issue.

One of our clients reported an issue where their (taxed) Membership Contributions were not being completed due to Paypal not accepting monetary amounts with 3 decimal places.

Steps to Reproduce:

1. Add a tax account with a 10% rate to Membership Dues
2. Create a Membership with a $145.45 (~$160) fee
3. Add a Contribution page with this membership
4. (Note contribution amount appears as 159.99 - adding a cent pushes it to $160.01)
5. Try to process payment via PayPal WPS

Expected Results: Successful payment, IPN callback, et cetera

Actual Results: Paypal refuses to process the payment, contribution is in pending state forever more.

This is a result of the amount actually being submitted as $159.995

From my investigation, it appears this can be rectified without ill effect by rounding the output of CRM_Contribute_BAO_Contributions_Utils::calculateTaxAmount to two decimal places.