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 $107.97   10.407%   $119.2064   $119.21   $119.20   $119.20  
  Purchase #2 $206.27   9.679%   $226.2349   $226.23   $226.25   $226.20  
  Purchase #3 $157.63   6.324%   $167.5985   $167.60   $167.60   $167.60  
  Purchase #4 $79.56   5.709%   $84.1021   $84.10   $84.10   $84.10  
  Purchase #5 $64.70   11.615%   $72.2149   $72.21   $72.20   $72.20  
  Purchase #6 $188.72   3.712%   $195.7253   $195.73   $195.75   $195.70  
  Purchase #7 $56.75   6.208%   $60.273   $60.27   $60.25   $60.30  
  7 purchase totals = $861.60       $925.3551   $925.35   $925.35   $925.30