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	$107.73	3.616%	$111.6255	$111.63	$111.65	$111.60
Purchase #2	$219.29	6.445%	$233.4232	$233.42	$233.40	$233.40
Purchase #3	$116.81	11.499%	$130.242	$130.24	$130.25	$130.20
Purchase #4	$166.49	3.756%	$172.7434	$172.74	$172.75	$172.70
Purchase #5	$75.70	10.463%	$83.6205	$83.62	$83.60	$83.60
Purchase #6	$191.37	8.105%	$206.8805	$206.88	$206.90	$206.90
Purchase #7	$195.62	7.389%	$210.0744	$210.07	$210.05	$210.10
7 purchase totals =	$1,073.01		$1,148.6095	$1,148.60	$1,148.60	$1,148.50