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 $118.93   5.661%   $125.6626   $125.66   $125.65   $125.70  
  Purchase #2 $35.85   13.216%   $40.5879   $40.59   $40.60   $40.60  
  Purchase #3 $224.49   3.696%   $232.7872   $232.79   $232.80   $232.80  
  Purchase #4 $44.80   5.116%   $47.092   $47.09   $47.10   $47.10  
  Purchase #5 $244.33   7.492%   $262.6352   $262.64   $262.65   $262.60  
  Purchase #6 $29.32   13.722%   $33.3433   $33.34   $33.35   $33.30  
  Purchase #7 $211.97   5.873%   $224.419   $224.42   $224.40   $224.40  
  7 purchase totals = $909.69       $966.5272   $966.53   $966.55   $966.50