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	$235.53	3.847%	$244.5908	$244.59	$244.60	$244.60
Purchase #2	$82.72	11.848%	$92.5207	$92.52	$92.50	$92.50
Purchase #3	$53.96	10.335%	$59.5368	$59.54	$59.55	$59.50
Purchase #4	$26.29	11.127%	$29.2153	$29.22	$29.20	$29.20
Purchase #5	$124.64	11.382%	$138.8265	$138.83	$138.85	$138.80
Purchase #6	$89.42	13.737%	$101.7036	$101.70	$101.70	$101.70
Purchase #7	$184.93	8.339%	$200.3513	$200.35	$200.35	$200.40
7 purchase totals =	$797.49		$866.7450	$866.75	$866.75	$866.70