do you think accepting bitcoin in Singapore will increase sales?
or it is absolutely useless?
You'll certainly get the novelty factor out of it and people will talk about it.
The main question is: Do you still want SGD at the end of the day or will want to you keep the BTC?
If the latter, just try it. You can get started with a cheap Android phone and the Mycelium app. Make a private key somewhere safe and use Mycelium to monitor the corresponding address. Whenever a customer comes along you or your staff can enter the SGD amount in Mycelium and it will convert using the data from the exchange of your choice. Customer scans the QR code - done. This will probably take 30 mins to an hour to setup. You always can move to a more sophisticated system later.
If you want fiat out of it, you'll have to talk to Coinpip. AFAIK they are currently the only merchant solution for SGD.