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 $239.43   8.688%   $260.2317   $260.23   $260.25   $260.20  
  Purchase #2 $242.54   4.558%   $253.595   $253.60   $253.60   $253.60  
  Purchase #3 $72.91   3.862%   $75.7258   $75.73   $75.75   $75.70  
  Purchase #4 $243.84   9.338%   $266.6098   $266.61   $266.60   $266.60  
  Purchase #5 $13.83   5.697%   $14.6179   $14.62   $14.60   $14.60  
  Purchase #6 $90.78   10.663%   $100.4599   $100.46   $100.45   $100.50  
  Purchase #7 $213.51   4.577%   $223.2824   $223.28   $223.30   $223.30  
  7 purchase totals = $1,116.84       $1,194.5225   $1,194.53   $1,194.55   $1,194.50