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 $115.49   3.353%   $119.3624   $119.36   $119.35   $119.40  
  Purchase #2 $236.70   3.317%   $244.5513   $244.55   $244.55   $244.60  
  Purchase #3 $174.44   4.767%   $182.7556   $182.76   $182.75   $182.80  
  Purchase #4 $42.63   7.598%   $45.869   $45.87   $45.85   $45.90  
  Purchase #5 $88.56   4.630%   $92.6603   $92.66   $92.65   $92.70  
  Purchase #6 $155.71   10.285%   $171.7248   $171.72   $171.70   $171.70  
  Purchase #7 $34.83   8.868%   $37.9187   $37.92   $37.90   $37.90  
  7 purchase totals = $848.36       $894.8421   $894.84   $894.75   $895.00