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 $110.69   10.565%   $122.3844   $122.38   $122.40   $122.40  
  Purchase #2 $173.69   13.209%   $196.6327   $196.63   $196.65   $196.60  
  Purchase #3 $245.38   7.872%   $264.6963   $264.70   $264.70   $264.70  
  Purchase #4 $66.97   7.155%   $71.7617   $71.76   $71.75   $71.80  
  Purchase #5 $43.61   10.147%   $48.0351   $48.04   $48.05   $48.00  
  Purchase #6 $58.29   4.477%   $60.8996   $60.90   $60.90   $60.90  
  Purchase #7 $124.56   4.858%   $130.6111   $130.61   $130.60   $130.60  
  7 purchase totals = $823.19       $895.0209   $895.02   $895.05   $895.00