Storewide price changes (one more try)

[idesyns]

I tried this in another forum, maybe it was the wrong one? Hopefully, this is the right place to post this.

 

Is there a way to make dollar amount, or percentage based price changes, without having to adjust the individual prices of all items in a store? Say I wanted to have a 15% off sale or to raise my prices $5.00 throughout the entire store. Is there an easy way to accomplish this change?

 

I have the "attribute sets" contribution installed if that helps at all. Maybe there is another add on that can help make the adjustment?

 

Thanks in advance for your help.