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 $224.76   12.828%   $253.5922   $253.59   $253.60   $253.60  
  Purchase #2 $43.66   4.668%   $45.698   $45.70   $45.70   $45.70  
  Purchase #3 $83.70   4.712%   $87.6439   $87.64   $87.65   $87.60  
  Purchase #4 $202.92   7.390%   $217.9158   $217.92   $217.90   $217.90  
  Purchase #5 $67.66   12.796%   $76.3178   $76.32   $76.30   $76.30  
  Purchase #6 $209.68   4.259%   $218.6103   $218.61   $218.60   $218.60  
  Purchase #7 $61.60   8.340%   $66.7374   $66.74   $66.75   $66.70  
  7 purchase totals = $893.98       $966.5154   $966.52   $966.50   $966.40