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	$105.59	5.713%	$111.6224	$111.62	$111.60	$111.60
Purchase #2	$62.61	13.664%	$71.165	$71.17	$71.15	$71.20
Purchase #3	$24.52	12.255%	$27.5249	$27.52	$27.50	$27.50
Purchase #4	$250.69	3.647%	$259.8327	$259.83	$259.85	$259.80
Purchase #5	$55.72	9.201%	$60.8468	$60.85	$60.85	$60.80
Purchase #6	$228.99	4.648%	$239.6335	$239.63	$239.65	$239.60
Purchase #7	$134.52	8.151%	$145.4847	$145.48	$145.50	$145.50
7 purchase totals =	$862.64		$916.1100	$916.10	$916.10	$916.00