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 $216.89   9.162%   $236.7615   $236.76   $236.75   $236.80  
  Purchase #2 $142.91   4.522%   $149.3724   $149.37   $149.35   $149.40  
  Purchase #3 $240.75   5.264%   $253.4231   $253.42   $253.40   $253.40  
  Purchase #4 $108.25   3.107%   $111.6133   $111.61   $111.60   $111.60  
  Purchase #5 $22.29   10.543%   $24.64   $24.64   $24.65   $24.60  
  Purchase #6 $100.53   8.242%   $108.8157   $108.82   $108.80   $108.80  
  Purchase #7 $64.92   8.404%   $70.3759   $70.38   $70.40   $70.40  
  7 purchase totals = $896.54       $955.0019   $955.00   $954.95   $955.00