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	$69.95	4.114%	$72.8277	$72.83	$72.85	$72.80
Purchase #2	$158.73	8.530%	$172.2697	$172.27	$172.25	$172.30
Purchase #3	$10.57	13.678%	$12.0158	$12.02	$12.00	$12.00
Purchase #4	$58.60	11.320%	$65.2335	$65.23	$65.25	$65.20
Purchase #5	$81.27	10.643%	$89.9196	$89.92	$89.90	$89.90
Purchase #6	$212.81	6.749%	$227.1725	$227.17	$227.15	$227.20
Purchase #7	$142.88	4.478%	$149.2782	$149.28	$149.30	$149.30
7 purchase totals =	$734.81		$788.7170	$788.72	$788.70	$788.70