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 $209.27   7.157%   $224.2475   $224.25   $224.25   $224.20  
  Purchase #2 $46.95   5.353%   $49.4632   $49.46   $49.45   $49.50  
  Purchase #3 $105.89   9.774%   $116.2397   $116.24   $116.25   $116.20  
  Purchase #4 $243.48   11.815%   $272.2472   $272.25   $272.25   $272.20  
  Purchase #5 $38.39   6.863%   $41.0247   $41.02   $41.00   $41.00  
  Purchase #6 $114.35   9.354%   $125.0463   $125.05   $125.05   $125.00  
  Purchase #7 $183.65   6.697%   $195.949   $195.95   $195.95   $195.90  
  7 purchase totals = $941.98       $1,024.2176   $1,024.22   $1,024.20   $1,024.00