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 $208.61   7.643%   $224.5541   $224.55   $224.55   $224.60  
  Purchase #2 $186.70   9.675%   $204.7632   $204.76   $204.75   $204.80  
  Purchase #3 $96.31   5.430%   $101.5396   $101.54   $101.55   $101.50  
  Purchase #4 $67.88   4.733%   $71.0928   $71.09   $71.10   $71.10  
  Purchase #5 $63.84   6.355%   $67.897   $67.90   $67.90   $67.90  
  Purchase #6 $160.69   3.758%   $166.7287   $166.73   $166.75   $166.70  
  Purchase #7 $191.93   8.332%   $207.9216   $207.92   $207.90   $207.90  
  7 purchase totals = $975.96       $1,044.4970   $1,044.49   $1,044.50   $1,044.50