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 $119.26   8.675%   $129.6058   $129.61   $129.60   $129.60  
  Purchase #2 $241.88   8.215%   $261.7504   $261.75   $261.75   $261.80  
  Purchase #3 $10.65   8.513%   $11.5566   $11.56   $11.55   $11.60  
  Purchase #4 $119.96   7.667%   $129.1573   $129.16   $129.15   $129.20  
  Purchase #5 $71.80   6.179%   $76.2365   $76.24   $76.25   $76.20  
  Purchase #6 $76.66   9.767%   $84.1474   $84.15   $84.15   $84.10  
  Purchase #7 $187.48   4.641%   $196.1809   $196.18   $196.20   $196.20  
  7 purchase totals = $827.69       $888.6349   $888.65   $888.65   $888.70