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 $59.65   3.268%   $61.5994   $61.60   $61.60   $61.60  
  Purchase #2 $158.34   12.749%   $178.5268   $178.53   $178.55   $178.50  
  Purchase #3 $132.48   6.155%   $140.6341   $140.63   $140.65   $140.60  
  Purchase #4 $117.72   5.548%   $124.2511   $124.25   $124.25   $124.30  
  Purchase #5 $249.75   6.303%   $265.4917   $265.49   $265.50   $265.50  
  Purchase #6 $146.77   8.714%   $159.5595   $159.56   $159.55   $159.60  
  Purchase #7 $245.70   7.795%   $264.8523   $264.85   $264.85   $264.90  
  7 purchase totals = $1,110.41       $1,194.9149   $1,194.91   $1,194.95   $1,195.00