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	$226.87	5.818%	$240.0693	$240.07	$240.05	$240.10
Purchase #2	$100.62	13.726%	$114.4311	$114.43	$114.45	$114.40
Purchase #3	$14.67	6.325%	$15.5979	$15.60	$15.60	$15.60
Purchase #4	$98.55	12.668%	$111.0343	$111.03	$111.05	$111.00
Purchase #5	$51.78	4.417%	$54.0671	$54.07	$54.05	$54.10
Purchase #6	$145.53	5.667%	$153.7772	$153.78	$153.80	$153.80
Purchase #7	$36.68	12.172%	$41.1447	$41.14	$41.15	$41.10
7 purchase totals =	$674.70		$730.1216	$730.12	$730.15	$730.10