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	$58.58	11.124%	$65.0964	$65.10	$65.10	$65.10
Purchase #2	$204.42	3.624%	$211.8282	$211.83	$211.85	$211.80
Purchase #3	$20.56	3.155%	$21.2087	$21.21	$21.20	$21.20
Purchase #4	$59.36	4.364%	$61.9505	$61.95	$61.95	$62.00
Purchase #5	$53.74	10.178%	$59.2097	$59.21	$59.20	$59.20
Purchase #6	$111.56	9.433%	$122.0835	$122.08	$122.10	$122.10
Purchase #7	$133.51	13.194%	$151.1253	$151.13	$151.15	$151.10
7 purchase totals =	$641.73		$692.5023	$692.51	$692.55	$692.50