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	$196.60	13.156%	$222.4647	$222.46	$222.45	$222.50
Purchase #2	$154.45	11.396%	$172.0511	$172.05	$172.05	$172.10
Purchase #3	$153.81	13.608%	$174.7405	$174.74	$174.75	$174.70
Purchase #4	$144.81	9.248%	$158.202	$158.20	$158.20	$158.20
Purchase #5	$163.78	4.726%	$171.5202	$171.52	$171.50	$171.50
Purchase #6	$151.97	10.276%	$167.5864	$167.59	$167.60	$167.60
Purchase #7	$134.46	11.361%	$149.736	$149.74	$149.75	$149.70
7 purchase totals =	$1,099.88		$1,216.3009	$1,216.30	$1,216.30	$1,216.30