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 $177.93   10.133%   $195.9596   $195.96   $195.95   $196.00  
  Purchase #2 $170.86   9.408%   $186.9345   $186.93   $186.95   $186.90  
  Purchase #3 $223.38   10.558%   $246.9645   $246.96   $246.95   $247.00  
  Purchase #4 $191.93   3.767%   $199.16   $199.16   $199.15   $199.20  
  Purchase #5 $50.42   13.168%   $57.0593   $57.06   $57.05   $57.10  
  Purchase #6 $48.25   5.169%   $50.744   $50.74   $50.75   $50.70  
  Purchase #7 $8.90   9.134%   $9.7129   $9.71   $9.70   $9.70  
  7 purchase totals = $871.67       $946.5348   $946.52   $946.50   $946.60