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 $239.76   9.383%   $262.2567   $262.26   $262.25   $262.30  
  Purchase #2 $119.97   4.721%   $125.6338   $125.63   $125.65   $125.60  
  Purchase #3 $190.41   12.724%   $214.6378   $214.64   $214.65   $214.60  
  Purchase #4 $248.50   4.283%   $259.1433   $259.14   $259.15   $259.10  
  Purchase #5 $69.67   6.631%   $74.2898   $74.29   $74.30   $74.30  
  Purchase #6 $152.77   9.134%   $166.724   $166.72   $166.70   $166.70  
  Purchase #7 $210.94   6.647%   $224.9612   $224.96   $224.95   $225.00  
  7 purchase totals = $1,232.02       $1,327.6466   $1,327.64   $1,327.65   $1,327.60