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 $197.84   5.593%   $208.9052   $208.91   $208.90   $208.90  
  Purchase #2 $207.72   8.104%   $224.5536   $224.55   $224.55   $224.60  
  Purchase #3 $116.49   5.500%   $122.897   $122.90   $122.90   $122.90  
  Purchase #4 $53.68   12.348%   $60.3084   $60.31   $60.30   $60.30  
  Purchase #5 $158.37   5.403%   $166.9267   $166.93   $166.95   $166.90  
  Purchase #6 $16.28   12.432%   $18.3039   $18.30   $18.30   $18.30  
  Purchase #7 $236.74   12.161%   $265.53   $265.53   $265.55   $265.50  
  7 purchase totals = $987.12       $1,067.4248   $1,067.43   $1,067.45   $1,067.40