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 $59.40   5.136%   $62.4508   $62.45   $62.45   $62.50  
  Purchase #2 $211.50   7.647%   $227.6734   $227.67   $227.65   $227.70  
  Purchase #3 $113.69   5.676%   $120.143   $120.14   $120.15   $120.10  
  Purchase #4 $9.38   8.618%   $10.1884   $10.19   $10.20   $10.20  
  Purchase #5 $60.35   9.821%   $66.277   $66.28   $66.30   $66.30  
  Purchase #6 $182.36   3.452%   $188.6551   $188.66   $188.65   $188.70  
  Purchase #7 $105.63   9.556%   $115.724   $115.72   $115.70   $115.70  
  7 purchase totals = $742.31       $791.1117   $791.11   $791.10   $791.20