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	$151.68	5.353%	$159.7994	$159.80	$159.80	$159.80
Purchase #2	$200.44	12.391%	$225.2765	$225.28	$225.30	$225.30
Purchase #3	$230.25	10.425%	$254.2536	$254.25	$254.25	$254.30
Purchase #4	$129.81	10.509%	$143.4517	$143.45	$143.45	$143.50
Purchase #5	$235.39	10.287%	$259.6046	$259.60	$259.60	$259.60
Purchase #6	$71.84	12.212%	$80.6131	$80.61	$80.60	$80.60
Purchase #7	$34.71	8.166%	$37.5444	$37.54	$37.55	$37.50
7 purchase totals =	$1,054.12		$1,160.5433	$1,160.53	$1,160.55	$1,160.60