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	$140.83	11.422%	$156.9156	$156.92	$156.90	$156.90
Purchase #2	$53.52	11.784%	$59.8268	$59.83	$59.85	$59.80
Purchase #3	$200.59	4.258%	$209.1311	$209.13	$209.15	$209.10
Purchase #4	$228.87	6.693%	$244.1883	$244.19	$244.20	$244.20
Purchase #5	$160.81	3.386%	$166.255	$166.26	$166.25	$166.30
Purchase #6	$158.25	11.697%	$176.7605	$176.76	$176.75	$176.80
Purchase #7	$17.41	4.521%	$18.1971	$18.20	$18.20	$18.20
7 purchase totals =	$960.28		$1,031.2744	$1,031.29	$1,031.30	$1,031.30