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 $195.82   5.176%   $205.9556   $205.96   $205.95   $206.00  
  Purchase #2 $238.64   12.439%   $268.3244   $268.32   $268.30   $268.30  
  Purchase #3 $168.48   3.315%   $174.0651   $174.07   $174.05   $174.10  
  Purchase #4 $166.49   13.197%   $188.4617   $188.46   $188.45   $188.50  
  Purchase #5 $127.62   13.149%   $144.4008   $144.40   $144.40   $144.40  
  Purchase #6 $70.87   3.213%   $73.1471   $73.15   $73.15   $73.10  
  Purchase #7 $28.73   6.189%   $30.5081   $30.51   $30.50   $30.50  
  7 purchase totals = $996.65       $1,084.8628   $1,084.87   $1,084.80   $1,084.90