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 $111.49   9.544%   $122.1306   $122.13   $122.15   $122.10  
  Purchase #2 $248.71   5.314%   $261.9264   $261.93   $261.95   $261.90  
  Purchase #3 $159.38   6.282%   $169.3923   $169.39   $169.40   $169.40  
  Purchase #4 $161.84   12.631%   $182.282   $182.28   $182.30   $182.30  
  Purchase #5 $54.52   8.443%   $59.1231   $59.12   $59.10   $59.10  
  Purchase #6 $200.97   5.390%   $211.8023   $211.80   $211.80   $211.80  
  Purchase #7 $138.52   9.333%   $151.4481   $151.45   $151.45   $151.40  
  7 purchase totals = $1,075.43       $1,158.1048   $1,158.10   $1,158.15   $1,158.00