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	$219.27	4.688%	$229.5494	$229.55	$229.55	$229.50
Purchase #2	$36.28	4.123%	$37.7758	$37.78	$37.80	$37.80
Purchase #3	$157.57	12.196%	$176.7872	$176.79	$176.80	$176.80
Purchase #4	$249.91	3.158%	$257.8022	$257.80	$257.80	$257.80
Purchase #5	$17.76	4.615%	$18.5796	$18.58	$18.60	$18.60
Purchase #6	$74.47	5.298%	$78.4154	$78.42	$78.40	$78.40
Purchase #7	$116.35	13.555%	$132.1212	$132.12	$132.10	$132.10
7 purchase totals =	$871.61		$931.0308	$931.04	$931.05	$931.00