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	$212.35	5.306%	$223.6173	$223.62	$223.60	$223.60
Purchase #2	$212.77	9.864%	$233.7576	$233.76	$233.75	$233.80
Purchase #3	$161.29	7.819%	$173.9013	$173.90	$173.90	$173.90
Purchase #4	$44.86	7.827%	$48.3712	$48.37	$48.35	$48.40
Purchase #5	$118.60	10.779%	$131.3839	$131.38	$131.40	$131.40
Purchase #6	$139.59	3.196%	$144.0513	$144.05	$144.05	$144.10
Purchase #7	$129.90	6.388%	$138.198	$138.20	$138.20	$138.20
7 purchase totals =	$1,019.36		$1,093.2806	$1,093.28	$1,093.25	$1,093.40