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	$162.46	7.198%	$174.1539	$174.15	$174.15	$174.20
Purchase #2	$124.99	6.535%	$133.1581	$133.16	$133.15	$133.20
Purchase #3	$186.25	7.836%	$200.8446	$200.84	$200.85	$200.80
Purchase #4	$211.46	10.525%	$233.7162	$233.72	$233.70	$233.70
Purchase #5	$9.81	13.619%	$11.146	$11.15	$11.15	$11.10
Purchase #6	$173.62	13.218%	$196.5691	$196.57	$196.55	$196.60
Purchase #7	$46.51	4.393%	$48.5532	$48.55	$48.55	$48.60
7 purchase totals =	$915.10		$998.1411	$998.14	$998.10	$998.20