Invoice Tax calculation not happening round up or correctly

Hi Team

Invoice tax round up not working correctly non functional currency . Scenario .. User created invoice with four Line …. Manage tax edit level selected percentage 6 % and updated Manage detail level one invoice line assign 6% and rest 3 line assign tax 8 % . eg. Invoice Line amount is available 9000 and 8 % tax need to calculation 720 but system always calculating the 719.95

thanks

Ravinder