How to expires SAP cookies upon logoff

For portal authentication, I utilize a 3rd-party system. Upon portal logoff, I feel that I need to expire any and all SAP cookies. The SAP cookies seem to persist even after Logoff, and there presence breaks my integration to the 3rd party system.

It appears that the following 5 SAP cookies need to be expired:

MYSAPSSO2

JSESSIONID

PD-ECC

PortalAlias

saplb_*

Has anyone developed code to expire SAP cookies sufficiently?

Thanks,

Kevin