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 $112.81   5.709%   $119.2503   $119.25   $119.25   $119.30  
  Purchase #2 $52.99   5.763%   $56.0438   $56.04   $56.05   $56.00  
  Purchase #3 $135.39   4.105%   $140.9478   $140.95   $140.95   $140.90  
  Purchase #4 $193.90   12.252%   $217.6566   $217.66   $217.65   $217.70  
  Purchase #5 $224.64   6.777%   $239.8639   $239.86   $239.85   $239.90  
  Purchase #6 $39.51   6.690%   $42.1532   $42.15   $42.15   $42.20  
  Purchase #7 $217.51   12.627%   $244.975   $244.98   $245.00   $245.00  
  7 purchase totals = $976.75       $1,060.8906   $1,060.89   $1,060.90   $1,061.00