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	$200.61	8.852%	$218.368	$218.37	$218.35	$218.40
Purchase #2	$212.70	11.370%	$236.884	$236.88	$236.90	$236.90
Purchase #3	$134.77	11.326%	$150.0341	$150.03	$150.05	$150.00
Purchase #4	$51.71	3.456%	$53.4971	$53.50	$53.50	$53.50
Purchase #5	$16.58	10.328%	$18.2924	$18.29	$18.30	$18.30
Purchase #6	$159.55	7.868%	$172.1034	$172.10	$172.10	$172.10
Purchase #7	$148.63	6.580%	$158.4099	$158.41	$158.40	$158.40
7 purchase totals =	$924.55		$1,007.5889	$1,007.58	$1,007.60	$1,007.60