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	$226.37	3.162%	$233.5278	$233.53	$233.55	$233.50
Purchase #2	$63.55	5.232%	$66.8749	$66.87	$66.85	$66.90
Purchase #3	$139.35	10.183%	$153.54	$153.54	$153.55	$153.50
Purchase #4	$186.63	11.568%	$208.2194	$208.22	$208.20	$208.20
Purchase #5	$95.33	10.673%	$105.5046	$105.50	$105.50	$105.50
Purchase #6	$123.72	3.153%	$127.6209	$127.62	$127.60	$127.60
Purchase #7	$12.74	8.806%	$13.8619	$13.86	$13.85	$13.90
7 purchase totals =	$847.69		$909.1495	$909.14	$909.10	$909.10