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 $94.57   4.275%   $98.6129   $98.61   $98.60   $98.60  
  Purchase #2 $209.95   3.297%   $216.8721   $216.87   $216.85   $216.90  
  Purchase #3 $41.63   11.496%   $46.4158   $46.42   $46.40   $46.40  
  Purchase #4 $153.42   12.147%   $172.0559   $172.06   $172.05   $172.10  
  Purchase #5 $65.86   3.228%   $67.986   $67.99   $68.00   $68.00  
  Purchase #6 $239.89   9.129%   $261.7896   $261.79   $261.80   $261.80  
  Purchase #7 $182.49   10.684%   $201.9872   $201.99   $202.00   $202.00  
  7 purchase totals = $987.81       $1,065.7195   $1,065.73   $1,065.70   $1,065.80