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	$99.83	11.258%	$111.0689	$111.07	$111.05	$111.10
Purchase #2	$185.63	10.789%	$205.6576	$205.66	$205.65	$205.70
Purchase #3	$10.28	10.185%	$11.327	$11.33	$11.35	$11.30
Purchase #4	$155.50	11.619%	$173.5675	$173.57	$173.55	$173.60
Purchase #5	$148.60	6.361%	$158.0524	$158.05	$158.05	$158.10
Purchase #6	$106.31	9.579%	$116.4934	$116.49	$116.50	$116.50
Purchase #7	$70.62	10.514%	$78.045	$78.05	$78.05	$78.00
7 purchase totals =	$776.77		$854.2118	$854.22	$854.20	$854.30