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 $25.62   3.473%   $26.5098   $26.51   $26.50   $26.50  
  Purchase #2 $200.98   4.303%   $209.6282   $209.63   $209.65   $209.60  
  Purchase #3 $236.89   3.610%   $245.4417   $245.44   $245.45   $245.40  
  Purchase #4 $165.93   6.724%   $177.0871   $177.09   $177.10   $177.10  
  Purchase #5 $224.63   9.484%   $245.9339   $245.93   $245.95   $245.90  
  Purchase #6 $60.74   5.662%   $64.1791   $64.18   $64.20   $64.20  
  Purchase #7 $126.53   6.257%   $134.447   $134.45   $134.45   $134.40  
  7 purchase totals = $1,041.32       $1,103.2268   $1,103.23   $1,103.30   $1,103.10