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 $35.95   5.563%   $37.9499   $37.95   $37.95   $37.90  
  Purchase #2 $231.67   5.633%   $244.72   $244.72   $244.70   $244.70  
  Purchase #3 $115.97   9.426%   $126.9013   $126.90   $126.90   $126.90  
  Purchase #4 $162.92   9.623%   $178.5978   $178.60   $178.60   $178.60  
  Purchase #5 $77.47   4.246%   $80.7594   $80.76   $80.75   $80.80  
  Purchase #6 $34.69   8.209%   $37.5377   $37.54   $37.55   $37.50  
  Purchase #7 $195.88   9.863%   $215.1996   $215.20   $215.20   $215.20  
  7 purchase totals = $854.55       $921.6657   $921.67   $921.65   $921.60