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	$105.45	5.872%	$111.642	$111.64	$111.65	$111.60
Purchase #2	$33.56	10.596%	$37.116	$37.12	$37.10	$37.10
Purchase #3	$87.43	3.456%	$90.4516	$90.45	$90.45	$90.50
Purchase #4	$10.84	4.345%	$11.311	$11.31	$11.30	$11.30
Purchase #5	$78.99	6.532%	$84.1496	$84.15	$84.15	$84.10
Purchase #6	$191.42	9.103%	$208.845	$208.85	$208.85	$208.80
Purchase #7	$222.31	9.260%	$242.8959	$242.90	$242.90	$242.90
7 purchase totals =	$730.00		$786.4111	$786.42	$786.40	$786.30