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	$178.45	12.410%	$200.5956	$200.60	$200.60	$200.60
Purchase #2	$108.47	3.515%	$112.2827	$112.28	$112.30	$112.30
Purchase #3	$69.45	12.694%	$78.266	$78.27	$78.25	$78.30
Purchase #4	$5.51	10.176%	$6.0707	$6.07	$6.05	$6.10
Purchase #5	$7.74	12.674%	$8.721	$8.72	$8.70	$8.70
Purchase #6	$11.65	5.724%	$12.3168	$12.32	$12.30	$12.30
Purchase #7	$175.60	8.274%	$190.1291	$190.13	$190.15	$190.10
7 purchase totals =	$556.87		$608.3819	$608.39	$608.35	$608.40