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	$159.62	8.766%	$173.6123	$173.61	$173.60	$173.60
Purchase #2	$214.40	3.259%	$221.3873	$221.39	$221.40	$221.40
Purchase #3	$9.32	5.327%	$9.8165	$9.82	$9.80	$9.80
Purchase #4	$64.59	10.784%	$71.5554	$71.56	$71.55	$71.60
Purchase #5	$132.72	8.364%	$143.8207	$143.82	$143.80	$143.80
Purchase #6	$142.51	4.654%	$149.1424	$149.14	$149.15	$149.10
Purchase #7	$33.72	11.446%	$37.5796	$37.58	$37.60	$37.60
7 purchase totals =	$756.88		$806.9142	$806.92	$806.90	$806.90