service tax

Hi Sap Guru's

I created account key and condition types for service tax and tax procedure also maintained

Serive tax 9%

Edu cess 2%

H edu cess 1%

But at the time of entry posting suppose Rs.100, the service tax amount not calculating properly.The  Amount 100 mean  service tax should be Rs.9, but it's calculating 8.24. Where i has done mistake

kindly advice me thanks full them.

Regards,

Ramesh