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	$56.31	5.224%	$59.2516	$59.25	$59.25	$59.30
Purchase #2	$110.75	5.162%	$116.4669	$116.47	$116.45	$116.50
Purchase #3	$85.50	9.672%	$93.7696	$93.77	$93.75	$93.80
Purchase #4	$49.62	9.859%	$54.512	$54.51	$54.50	$54.50
Purchase #5	$109.55	11.191%	$121.8097	$121.81	$121.80	$121.80
Purchase #6	$74.32	11.136%	$82.5963	$82.60	$82.60	$82.60
Purchase #7	$18.28	13.134%	$20.6809	$20.68	$20.70	$20.70
7 purchase totals =	$504.33		$549.0870	$549.09	$549.05	$549.20