How to round corners of ext-button?

[b1ackf1am3]

How to make rounded corners in ext-button?
I know button has 9 attributes in css

.x-btn-tl,
.x-btn-tr,
.x-btn-tc,

.x-btn-ml,
.x-btn-mr,
.x-btn-mc,

.x-btn-bl,
.x-btn-br,
.x-btn-bc

and i should probably set something on the tl,tr,bl,br to change corners styles, but what should it be?

[VadimV1144]

I would also really like to know this. Can anyone please help.

[bogusky]

Background image

.x-btn-tl, .x-btn-tr, .x-btn-tc, .x-btn-ml, .x-btn-mr, .x-btn-mc, .x-btn-bl, .x-btn-br, .x-btn-bc {
    background-image: url("../images/default/button/btn.gif");


}