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 $92.79   3.667%   $96.1926   $96.19   $96.20   $96.20  
  Purchase #2 $237.42   10.607%   $262.6031   $262.60   $262.60   $262.60  
  Purchase #3 $180.27   3.555%   $186.6786   $186.68   $186.70   $186.70  
  Purchase #4 $47.85   6.520%   $50.9698   $50.97   $50.95   $51.00  
  Purchase #5 $50.75   8.536%   $55.082   $55.08   $55.10   $55.10  
  Purchase #6 $194.65   12.187%   $218.372   $218.37   $218.35   $218.40  
  Purchase #7 $183.83   8.388%   $199.2497   $199.25   $199.25   $199.20  
  7 purchase totals = $987.56       $1,069.1478   $1,069.14   $1,069.15   $1,069.20