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	$10.76	4.505%	$11.2447	$11.24	$11.25	$11.20
Purchase #2	$78.65	4.459%	$82.157	$82.16	$82.15	$82.20
Purchase #3	$206.81	4.479%	$216.073	$216.07	$216.05	$216.10
Purchase #4	$99.65	11.716%	$111.325	$111.33	$111.35	$111.30
Purchase #5	$53.97	12.661%	$60.8031	$60.80	$60.80	$60.80
Purchase #6	$53.75	7.118%	$57.5759	$57.58	$57.60	$57.60
Purchase #7	$130.99	10.152%	$144.2881	$144.29	$144.30	$144.30
7 purchase totals =	$634.58		$683.4668	$683.47	$683.50	$683.50