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	$206.35	5.199%	$217.0781	$217.08	$217.10	$217.10
Purchase #2	$111.60	4.182%	$116.2671	$116.27	$116.25	$116.30
Purchase #3	$207.48	12.485%	$233.3839	$233.38	$233.40	$233.40
Purchase #4	$145.85	3.796%	$151.3865	$151.39	$151.40	$151.40
Purchase #5	$111.72	8.728%	$121.4709	$121.47	$121.45	$121.50
Purchase #6	$77.43	10.434%	$85.509	$85.51	$85.50	$85.50
Purchase #7	$154.70	8.274%	$167.4999	$167.50	$167.50	$167.50
7 purchase totals =	$1,015.13		$1,092.5954	$1,092.60	$1,092.60	$1,092.70