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 $212.99   6.442%   $226.7108   $226.71   $226.70   $226.70  
  Purchase #2 $41.91   6.339%   $44.5667   $44.57   $44.55   $44.60  
  Purchase #3 $141.66   3.602%   $146.7626   $146.76   $146.75   $146.80  
  Purchase #4 $88.71   7.865%   $95.687   $95.69   $95.70   $95.70  
  Purchase #5 $95.65   4.213%   $99.6797   $99.68   $99.70   $99.70  
  Purchase #6 $95.79   6.162%   $101.6926   $101.69   $101.70   $101.70  
  Purchase #7 $130.69   12.334%   $146.8093   $146.81   $146.80   $146.80  
  7 purchase totals = $807.40       $861.9087   $861.91   $861.90   $862.00