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 $205.54   4.118%   $214.0041   $214.00   $214.00   $214.00  
  Purchase #2 $196.66   6.125%   $208.7054   $208.71   $208.70   $208.70  
  Purchase #3 $200.69   10.615%   $221.9932   $221.99   $222.00   $222.00  
  Purchase #4 $81.99   13.620%   $93.157   $93.16   $93.15   $93.20  
  Purchase #5 $5.47   4.136%   $5.6962   $5.70   $5.70   $5.70  
  Purchase #6 $68.39   3.758%   $70.9601   $70.96   $70.95   $71.00  
  Purchase #7 $134.34   4.518%   $140.4095   $140.41   $140.40   $140.40  
  7 purchase totals = $893.08       $954.9255   $954.93   $954.90   $955.00