the 'roundest' chainrings are cut, the not so round are stamped. Just a matter of quality and from what I understand it is pretty common with lower end stamped rings. *edit* could be your rear cog also. Again, stamped or cut. Either way, maybe a bit faster wear on your driveline depending how not-round your combo is.

and as others will point out, make sure your not running too tight of tension. That helps alot too.