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 $82.69   13.743%   $94.0541   $94.05   $94.05   $94.10  
  Purchase #2 $196.50   10.558%   $217.2465   $217.25   $217.25   $217.20  
  Purchase #3 $151.35   6.677%   $161.4556   $161.46   $161.45   $161.50  
  Purchase #4 $51.49   3.292%   $53.1851   $53.19   $53.20   $53.20  
  Purchase #5 $161.64   10.409%   $178.4651   $178.47   $178.45   $178.50  
  Purchase #6 $113.95   9.537%   $124.8174   $124.82   $124.80   $124.80  
  Purchase #7 $53.64   9.330%   $58.6446   $58.64   $58.65   $58.60  
  7 purchase totals = $811.26       $887.8684   $887.88   $887.85   $887.90