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 $54.50   11.272%   $60.6432   $60.64   $60.65   $60.60  
  Purchase #2 $155.85   5.166%   $163.9012   $163.90   $163.90   $163.90  
  Purchase #3 $210.58   3.471%   $217.8892   $217.89   $217.90   $217.90  
  Purchase #4 $141.76   11.652%   $158.2779   $158.28   $158.30   $158.30  
  Purchase #5 $190.59   12.601%   $214.6062   $214.61   $214.60   $214.60  
  Purchase #6 $156.61   12.565%   $176.288   $176.29   $176.30   $176.30  
  Purchase #7 $72.72   5.786%   $76.9276   $76.93   $76.95   $76.90  
  7 purchase totals = $982.61       $1,068.5333   $1,068.54   $1,068.60   $1,068.50