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 $221.77   7.774%   $239.0104   $239.01   $239.00   $239.00  
  Purchase #2 $85.84   11.782%   $95.9537   $95.95   $95.95   $96.00  
  Purchase #3 $236.78   12.633%   $266.6924   $266.69   $266.70   $266.70  
  Purchase #4 $37.48   6.547%   $39.9338   $39.93   $39.95   $39.90  
  Purchase #5 $234.61   10.866%   $260.1027   $260.10   $260.10   $260.10  
  Purchase #6 $114.40   3.754%   $118.6946   $118.69   $118.70   $118.70  
  Purchase #7 $118.63   11.739%   $132.556   $132.56   $132.55   $132.60  
  7 purchase totals = $1,049.51       $1,152.9436   $1,152.93   $1,152.95   $1,153.00