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	$59.29	10.248%	$65.366	$65.37	$65.35	$65.40
Purchase #2	$153.44	11.343%	$170.8447	$170.84	$170.85	$170.80
Purchase #3	$210.70	10.859%	$233.5799	$233.58	$233.60	$233.60
Purchase #4	$112.69	4.838%	$118.1419	$118.14	$118.15	$118.10
Purchase #5	$117.41	5.740%	$124.1493	$124.15	$124.15	$124.10
Purchase #6	$39.64	9.103%	$43.2484	$43.25	$43.25	$43.20
Purchase #7	$162.67	13.810%	$185.1347	$185.13	$185.15	$185.10
7 purchase totals =	$855.84		$940.4649	$940.46	$940.50	$940.30