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	$118.92	3.569%	$123.1643	$123.16	$123.15	$123.20
Purchase #2	$210.54	8.793%	$229.0528	$229.05	$229.05	$229.10
Purchase #3	$94.42	6.866%	$100.9029	$100.90	$100.90	$100.90
Purchase #4	$9.57	5.535%	$10.0997	$10.10	$10.10	$10.10
Purchase #5	$111.66	10.434%	$123.3106	$123.31	$123.30	$123.30
Purchase #6	$228.51	4.211%	$238.1326	$238.13	$238.15	$238.10
Purchase #7	$58.41	7.136%	$62.5781	$62.58	$62.60	$62.60
7 purchase totals =	$832.03		$887.2410	$887.23	$887.25	$887.30