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	$214.56	4.250%	$223.6788	$223.68	$223.70	$223.70
Purchase #2	$105.71	8.338%	$114.5241	$114.52	$114.50	$114.50
Purchase #3	$183.90	8.252%	$199.0754	$199.08	$199.10	$199.10
Purchase #4	$180.45	6.335%	$191.8815	$191.88	$191.90	$191.90
Purchase #5	$238.85	11.624%	$266.6139	$266.61	$266.60	$266.60
Purchase #6	$113.67	4.748%	$119.0671	$119.07	$119.05	$119.10
Purchase #7	$74.76	9.870%	$82.1388	$82.14	$82.15	$82.10
7 purchase totals =	$1,111.90		$1,196.9796	$1,196.98	$1,197.00	$1,197.00