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	$78.72	11.151%	$87.4981	$87.50	$87.50	$87.50
Purchase #2	$9.67	9.507%	$10.5893	$10.59	$10.60	$10.60
Purchase #3	$54.37	5.439%	$57.3272	$57.33	$57.35	$57.30
Purchase #4	$169.91	3.485%	$175.8314	$175.83	$175.85	$175.80
Purchase #5	$157.46	10.349%	$173.7555	$173.76	$173.75	$173.80
Purchase #6	$83.30	5.230%	$87.6566	$87.66	$87.65	$87.70
Purchase #7	$64.89	13.612%	$73.7228	$73.72	$73.70	$73.70
7 purchase totals =	$618.32		$666.3809	$666.39	$666.40	$666.40