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 $41.69   5.716%   $44.073   $44.07   $44.05   $44.10  
  Purchase #2 $8.52   8.108%   $9.2108   $9.21   $9.20   $9.20  
  Purchase #3 $88.85   4.587%   $92.9255   $92.93   $92.95   $92.90  
  Purchase #4 $158.26   5.661%   $167.2191   $167.22   $167.20   $167.20  
  Purchase #5 $166.44   10.187%   $183.3952   $183.40   $183.40   $183.40  
  Purchase #6 $177.66   10.832%   $196.9041   $196.90   $196.90   $196.90  
  Purchase #7 $30.64   7.120%   $32.8216   $32.82   $32.80   $32.80  
  7 purchase totals = $672.06       $726.5493   $726.55   $726.50   $726.50