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 $214.55   5.646%   $226.6635   $226.66   $226.65   $226.70  
  Purchase #2 $16.81   8.522%   $18.2425   $18.24   $18.25   $18.20  
  Purchase #3 $119.82   4.606%   $125.3389   $125.34   $125.35   $125.30  
  Purchase #4 $86.96   4.573%   $90.9367   $90.94   $90.95   $90.90  
  Purchase #5 $190.36   8.472%   $206.4873   $206.49   $206.50   $206.50  
  Purchase #6 $232.85   12.716%   $262.4592   $262.46   $262.45   $262.50  
  Purchase #7 $192.64   4.870%   $202.0216   $202.02   $202.00   $202.00  
  7 purchase totals = $1,053.99       $1,132.1497   $1,132.15   $1,132.15   $1,132.10