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	$58.40	3.532%	$60.4627	$60.46	$60.45	$60.50
Purchase #2	$19.53	10.522%	$21.5849	$21.58	$21.60	$21.60
Purchase #3	$74.25	8.252%	$80.3771	$80.38	$80.40	$80.40
Purchase #4	$78.86	6.230%	$83.773	$83.77	$83.75	$83.80
Purchase #5	$144.52	4.518%	$151.0494	$151.05	$151.05	$151.00
Purchase #6	$153.38	13.565%	$174.186	$174.19	$174.20	$174.20
Purchase #7	$69.61	3.808%	$72.2607	$72.26	$72.25	$72.30
7 purchase totals =	$598.55		$643.6938	$643.69	$643.70	$643.80