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 $222.93   5.126%   $234.3574   $234.36   $234.35   $234.40  
  Purchase #2 $192.51   4.561%   $201.2904   $201.29   $201.30   $201.30  
  Purchase #3 $126.41   6.509%   $134.638   $134.64   $134.65   $134.60  
  Purchase #4 $24.61   6.624%   $26.2402   $26.24   $26.25   $26.20  
  Purchase #5 $148.68   10.710%   $164.6036   $164.60   $164.60   $164.60  
  Purchase #6 $241.89   8.302%   $261.9717   $261.97   $261.95   $262.00  
  Purchase #7 $231.76   6.237%   $246.2149   $246.21   $246.20   $246.20  
  7 purchase totals = $1,188.79       $1,269.3162   $1,269.31   $1,269.30   $1,269.30