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	$140.40	8.128%	$151.8117	$151.81	$151.80	$151.80
Purchase #2	$184.43	4.179%	$192.1373	$192.14	$192.15	$192.10
Purchase #3	$110.26	12.315%	$123.8385	$123.84	$123.85	$123.80
Purchase #4	$204.37	13.223%	$231.3938	$231.39	$231.40	$231.40
Purchase #5	$147.38	3.191%	$152.0829	$152.08	$152.10	$152.10
Purchase #6	$108.79	6.762%	$116.1464	$116.15	$116.15	$116.10
Purchase #7	$155.41	9.162%	$169.6487	$169.65	$169.65	$169.60
7 purchase totals =	$1,051.04		$1,137.0593	$1,137.06	$1,137.10	$1,136.90