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 $181.95   9.511%   $199.2553   $199.26   $199.25   $199.30  
  Purchase #2 $193.66   5.147%   $203.6277   $203.63   $203.65   $203.60  
  Purchase #3 $13.78   7.857%   $14.8627   $14.86   $14.85   $14.90  
  Purchase #4 $236.60   6.539%   $252.0713   $252.07   $252.05   $252.10  
  Purchase #5 $119.39   11.354%   $132.9455   $132.95   $132.95   $132.90  
  Purchase #6 $195.59   9.852%   $214.8595   $214.86   $214.85   $214.90  
  Purchase #7 $34.62   7.700%   $37.2857   $37.29   $37.30   $37.30  
  7 purchase totals = $975.59       $1,054.9077   $1,054.92   $1,054.90   $1,055.00