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	$111.78	4.599%	$116.9208	$116.92	$116.90	$116.90
Purchase #2	$38.65	11.616%	$43.1396	$43.14	$43.15	$43.10
Purchase #3	$172.94	13.112%	$195.6159	$195.62	$195.60	$195.60
Purchase #4	$20.75	3.110%	$21.3953	$21.40	$21.40	$21.40
Purchase #5	$50.65	3.544%	$52.445	$52.45	$52.45	$52.40
Purchase #6	$213.52	10.466%	$235.867	$235.87	$235.85	$235.90
Purchase #7	$18.91	7.448%	$20.3184	$20.32	$20.30	$20.30
7 purchase totals =	$627.20		$685.7020	$685.72	$685.65	$685.60