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 $68.83   10.360%   $75.9608   $75.96   $75.95   $76.00  
  Purchase #2 $160.89   12.211%   $180.5363   $180.54   $180.55   $180.50  
  Purchase #3 $42.51   8.794%   $46.2483   $46.25   $46.25   $46.20  
  Purchase #4 $194.53   13.723%   $221.2254   $221.23   $221.25   $221.20  
  Purchase #5 $14.41   4.867%   $15.1113   $15.11   $15.10   $15.10  
  Purchase #6 $131.96   6.491%   $140.5255   $140.53   $140.55   $140.50  
  Purchase #7 $71.75   3.734%   $74.4291   $74.43   $74.45   $74.40  
  7 purchase totals = $684.88       $754.0367   $754.05   $754.10   $753.90