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 $209.70   8.112%   $226.7109   $226.71   $226.70   $226.70  
  Purchase #2 $213.42   4.346%   $222.6952   $222.70   $222.70   $222.70  
  Purchase #3 $69.71   10.309%   $76.8964   $76.90   $76.90   $76.90  
  Purchase #4 $35.94   4.563%   $37.5799   $37.58   $37.60   $37.60  
  Purchase #5 $31.79   5.659%   $33.589   $33.59   $33.60   $33.60  
  Purchase #6 $214.66   4.634%   $224.6073   $224.61   $224.60   $224.60  
  Purchase #7 $139.98   3.804%   $145.3048   $145.30   $145.30   $145.30  
  7 purchase totals = $915.20       $967.3835   $967.39   $967.40   $967.40