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	$239.90	5.255%	$252.5067	$252.51	$252.50	$252.50
Purchase #2	$151.78	7.360%	$162.951	$162.95	$162.95	$163.00
Purchase #3	$118.27	10.743%	$130.9757	$130.98	$131.00	$131.00
Purchase #4	$99.28	12.716%	$111.9044	$111.90	$111.90	$111.90
Purchase #5	$106.52	4.481%	$111.2932	$111.29	$111.30	$111.30
Purchase #6	$145.57	3.396%	$150.5136	$150.51	$150.50	$150.50
Purchase #7	$208.55	7.195%	$223.5552	$223.56	$223.55	$223.60
7 purchase totals =	$1,069.87		$1,143.6998	$1,143.70	$1,143.70	$1,143.80