Is there a module for Free shipping only for gift certificate payment?

[eaglewu]

I want to avoid transaction fees or adding shipping fees for small transactions.

The purposes I want are:
1. If customers order less than $5 and pay by credit card, additional $0.5 will applied.
2. If customers order more than $5 and pay by credit card, no additional fee applies.
3. If customers order less than $5 and pay by gift certificate, no additional fee applies.

The additional $0.5 can be called as transaction fee or shipping fee.
Can anyone tell me how to fulfill?
Thanks,

eaglewu