Sales Tax Rounding error in Zen Cart 1.3.9d

I am running Zen Cart 1.3.9d. I have setup sales tax (VAT) and activated it for one product for testing purposes. I added this product to the basket and went through the checkout process. This is what was displayed:

Sub-Total:         £1.40
Shipping:          £2.50
VAT:               £0.25
Total:             £4.14

Sales Tax (VAT) is currently 17.5%. The VAT figure is 24.5p and is being rounded up to be £0.25, but the Total is rounded down (£4.14), so the figures do not appear to add up correctly - 1.40 + 2.50 + 0.25 should = 4.15 not 4.14.

Is this a known bug? Is there or will there be a fix for it?

Thank you.

There were taxation fixes in v1.3.9e, released earlier this week: http://www.zen-cart.com/forum/showthread.php?t=160378

Thank you Dr Byte. I'll work towards upgrading to 1.3.8.e.