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	$103.43	4.178%	$107.7513	$107.75	$107.75	$107.80
Purchase #2	$160.30	11.810%	$179.2314	$179.23	$179.25	$179.20
Purchase #3	$48.66	13.335%	$55.1488	$55.15	$55.15	$55.10
Purchase #4	$92.45	7.372%	$99.2654	$99.27	$99.25	$99.30
Purchase #5	$191.80	10.841%	$212.593	$212.59	$212.60	$212.60
Purchase #6	$41.64	9.218%	$45.4784	$45.48	$45.50	$45.50
Purchase #7	$176.58	8.784%	$192.0908	$192.09	$192.10	$192.10
7 purchase totals =	$814.86		$891.5591	$891.56	$891.60	$891.60