Designing a discount coupon.

Create a rounded rectangle using rounded rectangle shape tool.

Use radious as 20 pixels before creating.

Double click the layer to open layer style window. Apply settings as shown. Click on "styles" on top left. Click on small arrow from the right and choose Dotted Strokes. a palette will come with various styles of dotted strokes.

Select Black 1 pt-3pt Dashed fill from the palette.