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 $89.56   5.766%   $94.724   $94.72   $94.70   $94.70  
  Purchase #2 $218.49   3.548%   $226.242   $226.24   $226.25   $226.20  
  Purchase #3 $234.38   4.170%   $244.1536   $244.15   $244.15   $244.20  
  Purchase #4 $240.96   8.449%   $261.3187   $261.32   $261.30   $261.30  
  Purchase #5 $155.55   5.669%   $164.3681   $164.37   $164.35   $164.40  
  Purchase #6 $59.87   4.427%   $62.5204   $62.52   $62.50   $62.50  
  Purchase #7 $19.48   12.814%   $21.9762   $21.98   $22.00   $22.00  
  7 purchase totals = $1,018.29       $1,075.3030   $1,075.30   $1,075.25   $1,075.30