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	$127.92	13.854%	$145.642	$145.64	$145.65	$145.60
Purchase #2	$94.68	8.334%	$102.5706	$102.57	$102.55	$102.60
Purchase #3	$223.40	8.585%	$242.5789	$242.58	$242.60	$242.60
Purchase #4	$50.57	3.760%	$52.4714	$52.47	$52.45	$52.50
Purchase #5	$81.40	9.393%	$89.0459	$89.05	$89.05	$89.00
Purchase #6	$66.67	5.763%	$70.5122	$70.51	$70.50	$70.50
Purchase #7	$156.83	10.289%	$172.9662	$172.97	$172.95	$173.00
7 purchase totals =	$801.47		$875.7872	$875.79	$875.75	$875.80