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	$145.94	3.778%	$151.4536	$151.45	$151.45	$151.50
Purchase #2	$230.34	5.228%	$242.3822	$242.38	$242.40	$242.40
Purchase #3	$241.78	8.622%	$262.6263	$262.63	$262.65	$262.60
Purchase #4	$17.72	6.865%	$18.9365	$18.94	$18.95	$18.90
Purchase #5	$155.67	4.338%	$162.423	$162.42	$162.40	$162.40
Purchase #6	$214.89	10.808%	$238.1153	$238.12	$238.10	$238.10
Purchase #7	$216.80	5.592%	$228.9235	$228.92	$228.90	$228.90
7 purchase totals =	$1,223.14		$1,304.8604	$1,304.86	$1,304.85	$1,304.80