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 $65.53   11.789%   $73.2553   $73.26   $73.25   $73.30  
  Purchase #2 $111.59   5.403%   $117.6192   $117.62   $117.60   $117.60  
  Purchase #3 $168.71   11.473%   $188.0661   $188.07   $188.05   $188.10  
  Purchase #4 $44.70   13.474%   $50.7229   $50.72   $50.70   $50.70  
  Purchase #5 $169.62   12.238%   $190.3781   $190.38   $190.40   $190.40  
  Purchase #6 $141.88   8.401%   $153.7993   $153.80   $153.80   $153.80  
  Purchase #7 $175.49   7.529%   $188.7026   $188.70   $188.70   $188.70  
  7 purchase totals = $877.52       $962.5435   $962.55   $962.50   $962.60