Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $114.51   3.460%   $118.472   $118.47   $118.45   $118.50  
  Purchase #2 $218.60   12.343%   $245.5818   $245.58   $245.60   $245.60  
  Purchase #3 $44.38   7.422%   $47.6739   $47.67   $47.65   $47.70  
  Purchase #4 $103.47   3.379%   $106.9663   $106.97   $106.95   $107.00  
  Purchase #5 $13.88   10.108%   $15.283   $15.28   $15.30   $15.30  
  Purchase #6 $129.56   7.554%   $139.347   $139.35   $139.35   $139.30  
  Purchase #7 $84.61   8.728%   $91.9948   $91.99   $92.00   $92.00  
  7 purchase totals = $709.01       $765.3188   $765.31   $765.30   $765.40