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 $106.49   7.360%   $114.3277   $114.33   $114.35   $114.30  
  Purchase #2 $141.68   8.733%   $154.0529   $154.05   $154.05   $154.10  
  Purchase #3 $97.71   10.779%   $108.2422   $108.24   $108.25   $108.20  
  Purchase #4 $244.52   3.697%   $253.5599   $253.56   $253.55   $253.60  
  Purchase #5 $49.25   12.449%   $55.3811   $55.38   $55.40   $55.40  
  Purchase #6 $113.77   8.794%   $123.7749   $123.77   $123.75   $123.80  
  Purchase #7 $209.67   8.654%   $227.8148   $227.81   $227.80   $227.80  
  7 purchase totals = $963.09       $1,037.1535   $1,037.14   $1,037.15   $1,037.20