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 $204.27   11.125%   $226.995   $227.00   $227.00   $227.00  
  Purchase #2 $225.79   5.221%   $237.5785   $237.58   $237.60   $237.60  
  Purchase #3 $76.54   8.409%   $82.9762   $82.98   $83.00   $83.00  
  Purchase #4 $249.97   4.473%   $261.1512   $261.15   $261.15   $261.20  
  Purchase #5 $212.59   9.404%   $232.582   $232.58   $232.60   $232.60  
  Purchase #6 $131.67   4.272%   $137.2949   $137.29   $137.30   $137.30  
  Purchase #7 $61.26   9.854%   $67.2966   $67.30   $67.30   $67.30  
  7 purchase totals = $1,162.09       $1,245.8744   $1,245.88   $1,245.95   $1,246.00