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	$153.81	9.367%	$168.2174	$168.22	$168.20	$168.20
Purchase #2	$211.76	6.617%	$225.7722	$225.77	$225.75	$225.80
Purchase #3	$224.59	6.488%	$239.1614	$239.16	$239.15	$239.20
Purchase #4	$234.74	7.720%	$252.8619	$252.86	$252.85	$252.90
Purchase #5	$106.52	4.783%	$111.6149	$111.61	$111.60	$111.60
Purchase #6	$113.33	12.805%	$127.8419	$127.84	$127.85	$127.80
Purchase #7	$63.54	11.798%	$71.0364	$71.04	$71.05	$71.00
7 purchase totals =	$1,108.29		$1,196.5061	$1,196.50	$1,196.45	$1,196.50