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 $86.99   9.530%   $95.2801   $95.28   $95.30   $95.30  
  Purchase #2 $137.98   4.202%   $143.7779   $143.78   $143.80   $143.80  
  Purchase #3 $96.51   10.507%   $106.6503   $106.65   $106.65   $106.70  
  Purchase #4 $10.71   7.624%   $11.5265   $11.53   $11.55   $11.50  
  Purchase #5 $193.42   10.870%   $214.4448   $214.44   $214.45   $214.40  
  Purchase #6 $241.59   8.561%   $262.2725   $262.27   $262.25   $262.30  
  Purchase #7 $169.55   12.372%   $190.5267   $190.53   $190.55   $190.50  
  7 purchase totals = $936.75       $1,024.4788   $1,024.48   $1,024.55   $1,024.50