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 $214.92   12.549%   $241.8903   $241.89   $241.90   $241.90  
  Purchase #2 $130.38   4.617%   $136.3996   $136.40   $136.40   $136.40  
  Purchase #3 $167.76   4.557%   $175.4048   $175.40   $175.40   $175.40  
  Purchase #4 $146.74   4.578%   $153.4578   $153.46   $153.45   $153.50  
  Purchase #5 $31.55   9.107%   $34.4233   $34.42   $34.40   $34.40  
  Purchase #6 $88.61   9.714%   $97.2176   $97.22   $97.20   $97.20  
  Purchase #7 $104.57   9.871%   $114.8921   $114.89   $114.90   $114.90  
  7 purchase totals = $884.53       $953.6855   $953.68   $953.65   $953.70