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	$58.35	11.471%	$65.0433	$65.04	$65.05	$65.00
Purchase #2	$45.97	13.439%	$52.1479	$52.15	$52.15	$52.10
Purchase #3	$250.58	11.719%	$279.9455	$279.95	$279.95	$279.90
Purchase #4	$27.72	3.123%	$28.5857	$28.59	$28.60	$28.60
Purchase #5	$48.58	6.827%	$51.8966	$51.90	$51.90	$51.90
Purchase #6	$231.45	11.492%	$258.0482	$258.05	$258.05	$258.00
Purchase #7	$43.40	6.326%	$46.1455	$46.15	$46.15	$46.10
7 purchase totals =	$706.05		$781.8127	$781.83	$781.85	$781.60