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	$237.46	13.536%	$269.6026	$269.60	$269.60	$269.60
Purchase #2	$245.29	4.251%	$255.7173	$255.72	$255.70	$255.70
Purchase #3	$200.61	11.536%	$223.7524	$223.75	$223.75	$223.80
Purchase #4	$161.47	6.764%	$172.3918	$172.39	$172.40	$172.40
Purchase #5	$64.72	12.358%	$72.7181	$72.72	$72.70	$72.70
Purchase #6	$176.96	4.597%	$185.0949	$185.09	$185.10	$185.10
Purchase #7	$157.76	9.770%	$173.1732	$173.17	$173.15	$173.20
7 purchase totals =	$1,244.27		$1,352.4503	$1,352.44	$1,352.40	$1,352.50