The Collaborative International Dictionary of English v.0.48:

Exactness \Ex*act"ness\, n.
   1. The condition of being exact; accuracy; nicety; precision;
      regularity; as, exactness of judgement or deportment.
      [1913 Webster]

   2. Careful observance of method and conformity to truth; as,
      exactness in accounts or business.
      [1913 Webster]

            He had . . . that sort of exactness which would have
            made him a respectable antiquary.     --Macaulay.
      [1913 Webster]

WordNet (r) 3.0 (2006):

exactness
    n 1: the quality of being exact; "he demanded exactness in all
         details"; "a man of great exactitude" [syn: exactness,
         exactitude] [ant: inexactitude, inexactness]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "exactness":
   absoluteness, accuracy, attention to detail, attention to fact,
   care for truth, circumstantiality, conscientiousness, correctness,
   criticality, criticalness, definiteness, delicacy, detail,
   exactingness, exactitude, exquisiteness, faithfulness,
   faultlessness, fidelity, fineness, finicality, finicalness,
   finickiness, finickingness, flawlessness, fussiness, literalism,
   literality, literalness, mathematical precision, meticulousness,
   minuteness, niceness, nicety, particularity, particularness,
   perfection, preciseness, precisianism, precision, punctiliousness,
   punctuality, refinement, right, rightness, rigidity, rigidness,
   rigor, rigorousness, scrupulosity, scrupulousness, severity,
   strictness, subtlety, textualism, the letter