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	$223.71	13.413%	$253.7162	$253.72	$253.70	$253.70
Purchase #2	$39.98	12.786%	$45.0918	$45.09	$45.10	$45.10
Purchase #3	$100.49	8.164%	$108.694	$108.69	$108.70	$108.70
Purchase #4	$173.82	9.602%	$190.5102	$190.51	$190.50	$190.50
Purchase #5	$124.39	6.125%	$132.0089	$132.01	$132.00	$132.00
Purchase #6	$191.82	8.671%	$208.4527	$208.45	$208.45	$208.50
Purchase #7	$154.85	3.627%	$160.4664	$160.47	$160.45	$160.50
7 purchase totals =	$1,009.06		$1,098.9402	$1,098.94	$1,098.90	$1,099.00