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 $244.82   7.335%   $262.7775   $262.78   $262.80   $262.80  
  Purchase #2 $148.94   9.228%   $162.6842   $162.68   $162.70   $162.70  
  Purchase #3 $6.39   7.232%   $6.8521   $6.85   $6.85   $6.90  
  Purchase #4 $69.52   9.667%   $76.2405   $76.24   $76.25   $76.20  
  Purchase #5 $242.66   7.217%   $260.1728   $260.17   $260.15   $260.20  
  Purchase #6 $119.86   10.739%   $132.7318   $132.73   $132.75   $132.70  
  Purchase #7 $229.37   13.396%   $260.0964   $260.10   $260.10   $260.10  
  7 purchase totals = $1,061.56       $1,161.5553   $1,161.55   $1,161.60   $1,161.60