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 $234.25   11.766%   $261.8119   $261.81   $261.80   $261.80  
  Purchase #2 $224.56   3.343%   $232.067   $232.07   $232.05   $232.10  
  Purchase #3 $197.71   12.267%   $221.9631   $221.96   $221.95   $222.00  
  Purchase #4 $106.44   12.599%   $119.8504   $119.85   $119.85   $119.90  
  Purchase #5 $231.58   6.311%   $246.195   $246.20   $246.20   $246.20  
  Purchase #6 $239.62   13.377%   $271.674   $271.67   $271.65   $271.70  
  Purchase #7 $133.46   9.220%   $145.765   $145.77   $145.75   $145.80  
  7 purchase totals = $1,367.62       $1,499.3264   $1,499.33   $1,499.25   $1,499.50