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 $55.61   11.253%   $61.8678   $61.87   $61.85   $61.90  
  Purchase #2 $183.57   7.232%   $196.8458   $196.85   $196.85   $196.80  
  Purchase #3 $66.85   13.673%   $75.9904   $75.99   $76.00   $76.00  
  Purchase #4 $127.83   11.395%   $142.3962   $142.40   $142.40   $142.40  
  Purchase #5 $78.76   9.704%   $86.4029   $86.40   $86.40   $86.40  
  Purchase #6 $20.28   8.636%   $22.0314   $22.03   $22.05   $22.00  
  Purchase #7 $167.68   5.834%   $177.4625   $177.46   $177.45   $177.50  
  7 purchase totals = $700.58       $762.9970   $763.00   $763.00   $763.00