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 $63.56   11.200%   $70.6787   $70.68   $70.70   $70.70  
  Purchase #2 $97.37   3.738%   $101.0097   $101.01   $101.00   $101.00  
  Purchase #3 $220.84   11.534%   $246.3117   $246.31   $246.30   $246.30  
  Purchase #4 $232.75   7.209%   $249.5289   $249.53   $249.55   $249.50  
  Purchase #5 $215.66   9.541%   $236.2361   $236.24   $236.25   $236.20  
  Purchase #6 $36.59   9.630%   $40.1136   $40.11   $40.10   $40.10  
  Purchase #7 $236.38   10.496%   $261.1904   $261.19   $261.20   $261.20  
  7 purchase totals = $1,103.15       $1,205.0691   $1,205.07   $1,205.10   $1,205.00