nothing to worry about. you can send a bank draft in US dollars, or in ghanaian cedis.
see, they even say that in their website:
http://www.dfait-maeci.gc.ca/accra/immig-fees-en.asp
Method of Payment
Fees must be submitted in person or by mail to the Immigration Section of the Canadian High Commission in Accra. Only the following forms of payment, in Ghanaian, U.S. or Canadian funds, are acceptable:
* Certified Cheque
* Bank Draft
***Note: We do not accept personal cheques
Specific instructions on submitting fees
* Bank drafts and certified cheques must be correctly addressed:
o Canadian or US funds: Bank drafts and certified cheques in Canadian or US funds must be made payable to: "The Receiver General for Canada". They must bear the name of a correspondent bank in North America.
o Ghanaian Cedis: Bank drafts and certified cheques in Ghanaian Cedis must be made payable to: "The Canadian High Commission"
* Certified cheques or drafts with a validity of less than 6 months will not be accepted.