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 $23.84   7.372%   $25.5975   $25.60   $25.60   $25.60  
  Purchase #2 $212.89   12.765%   $240.0654   $240.07   $240.05   $240.10  
  Purchase #3 $185.87   9.786%   $204.0592   $204.06   $204.05   $204.10  
  Purchase #4 $218.85   8.679%   $237.844   $237.84   $237.85   $237.80  
  Purchase #5 $163.98   7.439%   $176.1785   $176.18   $176.20   $176.20  
  Purchase #6 $250.73   4.769%   $262.6873   $262.69   $262.70   $262.70  
  Purchase #7 $190.53   8.397%   $206.5288   $206.53   $206.55   $206.50  
  7 purchase totals = $1,246.69       $1,352.9607   $1,352.97   $1,353.00   $1,353.00