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 $117.81   6.324%   $125.2603   $125.26   $125.25   $125.30  
  Purchase #2 $153.88   12.823%   $173.612   $173.61   $173.60   $173.60  
  Purchase #3 $227.42   13.559%   $258.2559   $258.26   $258.25   $258.30  
  Purchase #4 $199.67   12.415%   $224.459   $224.46   $224.45   $224.50  
  Purchase #5 $51.98   3.251%   $53.6699   $53.67   $53.65   $53.70  
  Purchase #6 $235.25   10.260%   $259.3867   $259.39   $259.40   $259.40  
  Purchase #7 $220.49   12.649%   $248.3798   $248.38   $248.40   $248.40  
  7 purchase totals = $1,206.50       $1,343.0236   $1,343.03   $1,343.00   $1,343.20