Any small business accounting software will do. You could try online accounting software like ours - Clarity Accounting - or a desktop application like QuickBooks. Both have their advantages and disadvantages - desktop software generally requires more training and is harder to use, but it also has more features since it has been around for longer.
Clarity Accounting does support Singapore dollars. I'm not sure if QuickBooks is available in Singapore - I suspect you might be stuck with MYOB if you want desktop software, which I've only heard bad things about. There are some other web-based accounting application in that area, but I don't know how friendly they are to Singapore users, like http://xero.com.