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	$10.70	11.719%	$11.9539	$11.95	$11.95	$12.00
Purchase #2	$192.55	10.415%	$212.6041	$212.60	$212.60	$212.60
Purchase #3	$101.61	3.374%	$105.0383	$105.04	$105.05	$105.00
Purchase #4	$230.75	10.733%	$255.5164	$255.52	$255.50	$255.50
Purchase #5	$90.97	9.760%	$99.8487	$99.85	$99.85	$99.80
Purchase #6	$56.93	3.824%	$59.107	$59.11	$59.10	$59.10
Purchase #7	$141.91	5.806%	$150.1493	$150.15	$150.15	$150.10
7 purchase totals =	$825.42		$894.2177	$894.22	$894.20	$894.10