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	$200.74	8.368%	$217.5379	$217.54	$217.55	$217.50
Purchase #2	$19.71	5.360%	$20.7665	$20.77	$20.75	$20.80
Purchase #3	$62.82	4.396%	$65.5816	$65.58	$65.60	$65.60
Purchase #4	$26.92	4.287%	$28.0741	$28.07	$28.05	$28.10
Purchase #5	$43.31	11.114%	$48.1235	$48.12	$48.10	$48.10
Purchase #6	$30.50	10.149%	$33.5954	$33.60	$33.60	$33.60
Purchase #7	$157.70	9.149%	$172.128	$172.13	$172.15	$172.10
7 purchase totals =	$541.70		$585.8070	$585.81	$585.80	$585.80