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	$121.73	4.593%	$127.3211	$127.32	$127.30	$127.30
Purchase #2	$111.67	13.702%	$126.971	$126.97	$126.95	$127.00
Purchase #3	$39.43	8.257%	$42.6857	$42.69	$42.70	$42.70
Purchase #4	$146.29	13.233%	$165.6486	$165.65	$165.65	$165.60
Purchase #5	$210.76	13.162%	$238.5002	$238.50	$238.50	$238.50
Purchase #6	$150.42	10.209%	$165.7764	$165.78	$165.80	$165.80
Purchase #7	$79.71	7.470%	$85.6643	$85.66	$85.65	$85.70
7 purchase totals =	$860.01		$952.5673	$952.57	$952.55	$952.60