The Collaborative International Dictionary of English v.0.48:

Quits \Quits\ (kw[i^]ts), interj.
   See the Note under Quit, a.
   [1913 Webster]

WordNet (r) 3.0 (2006):

quits
    adj 1: on equal terms by payment or requital; "we're now quits";
           "finally quits with the loan"

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "quits":
   alike, at par, au pair, commensurate, drawn, equal, equalized,
   even, even stephen, fifty-fifty, half-and-half, knotted, level,
   like, nip and tuck, on a footing, on a level, on a par,
   on even ground, par, proportionate, square, stalemated, tied