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 $71.48   7.195%   $76.623   $76.62   $76.60   $76.60  
  Purchase #2 $152.27   5.629%   $160.8413   $160.84   $160.85   $160.80  
  Purchase #3 $227.28   4.102%   $236.603   $236.60   $236.60   $236.60  
  Purchase #4 $62.63   6.219%   $66.525   $66.53   $66.55   $66.50  
  Purchase #5 $66.54   12.639%   $74.95   $74.95   $74.95   $75.00  
  Purchase #6 $169.55   8.437%   $183.8549   $183.85   $183.85   $183.90  
  Purchase #7 $201.96   8.260%   $218.6419   $218.64   $218.65   $218.60  
  7 purchase totals = $951.71       $1,018.0391   $1,018.03   $1,018.05   $1,018.00