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	$107.31	3.525%	$111.0927	$111.09	$111.10	$111.10
Purchase #2	$163.44	5.491%	$172.4145	$172.41	$172.40	$172.40
Purchase #3	$122.50	5.659%	$129.4323	$129.43	$129.45	$129.40
Purchase #4	$173.28	7.434%	$186.1616	$186.16	$186.15	$186.20
Purchase #5	$93.67	11.108%	$104.0749	$104.07	$104.05	$104.10
Purchase #6	$248.95	5.811%	$263.4165	$263.42	$263.40	$263.40
Purchase #7	$83.34	13.558%	$94.6392	$94.64	$94.65	$94.60
7 purchase totals =	$992.49		$1,061.2317	$1,061.22	$1,061.20	$1,061.20