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 $94.84   3.391%   $98.056   $98.06   $98.05   $98.10  
  Purchase #2 $196.62   12.476%   $221.1503   $221.15   $221.15   $221.20  
  Purchase #3 $148.39   12.328%   $166.6835   $166.68   $166.70   $166.70  
  Purchase #4 $193.66   12.758%   $218.3671   $218.37   $218.35   $218.40  
  Purchase #5 $119.75   10.708%   $132.5728   $132.57   $132.55   $132.60  
  Purchase #6 $121.86   5.237%   $128.2418   $128.24   $128.25   $128.20  
  Purchase #7 $69.83   12.496%   $78.556   $78.56   $78.55   $78.60  
  7 purchase totals = $944.95       $1,043.6275   $1,043.63   $1,043.60   $1,043.80