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	$212.98	8.305%	$230.668	$230.67	$230.65	$230.70
Purchase #2	$206.27	13.367%	$233.8421	$233.84	$233.85	$233.80
Purchase #3	$105.91	10.681%	$117.2222	$117.22	$117.20	$117.20
Purchase #4	$176.90	7.472%	$190.118	$190.12	$190.10	$190.10
Purchase #5	$193.51	12.426%	$217.5556	$217.56	$217.55	$217.60
Purchase #6	$74.32	5.336%	$78.2857	$78.29	$78.30	$78.30
Purchase #7	$84.88	5.810%	$89.8115	$89.81	$89.80	$89.80
7 purchase totals =	$1,054.77		$1,157.5031	$1,157.51	$1,157.45	$1,157.50