The actress' original script from the film was also among the items at the sale in Beverly Hills, California, which in total raised $2.4m.
Some of the proceeds will go towards Newton-John's cancer treatment centre in Australia.
The buyers' identities are not public.
Grease was released in 1978 and Olivia Newton-John played demure Sandy alongside John Travolta as bad boy Danny.
The infamous black outfit marked Sandy's transition from a good girl high-schooler to a sexy, leather-clad biker chick, when the couple sang You're the One That I Want in a fairground.