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	$134.40	10.220%	$148.1357	$148.14	$148.15	$148.10
Purchase #2	$92.83	12.172%	$104.1293	$104.13	$104.15	$104.10
Purchase #3	$217.94	13.678%	$247.7498	$247.75	$247.75	$247.70
Purchase #4	$107.42	3.525%	$111.2066	$111.21	$111.20	$111.20
Purchase #5	$145.51	5.413%	$153.3865	$153.39	$153.40	$153.40
Purchase #6	$137.73	10.304%	$151.9217	$151.92	$151.90	$151.90
Purchase #7	$159.99	3.743%	$165.9784	$165.98	$166.00	$166.00
7 purchase totals =	$995.82		$1,082.5080	$1,082.52	$1,082.55	$1,082.40