So I figured out a way to get the behavior I am looking for:
tiddlywiki –render "[tag[post]]" "[has[created]lowercase[]escaperegexp[]splitregexp[ ]join[-]encodeuricomponent[]addsuffix[.html]]" "text/plain" "$:/blog-post/templates/static.tiddler.html"
basically this creates a uri with hyphens and all lowercase from the title of tiddlers tagged posted instead of the %20 for spaces which I think is really ugly. a small thing I know but it was bugging me.