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	$173.95	7.749%	$187.4294	$187.43	$187.45	$187.40
Purchase #2	$132.38	12.243%	$148.5873	$148.59	$148.60	$148.60
Purchase #3	$15.30	4.437%	$15.9789	$15.98	$16.00	$16.00
Purchase #4	$19.27	12.773%	$21.7314	$21.73	$21.75	$21.70
Purchase #5	$127.51	13.419%	$144.6206	$144.62	$144.60	$144.60
Purchase #6	$144.92	4.796%	$151.8704	$151.87	$151.85	$151.90
Purchase #7	$17.38	3.866%	$18.0519	$18.05	$18.05	$18.10
7 purchase totals =	$630.71		$688.2699	$688.27	$688.30	$688.30