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	$166.71	10.192%	$183.7011	$183.70	$183.70	$183.70
Purchase #2	$128.25	12.393%	$144.144	$144.14	$144.15	$144.10
Purchase #3	$154.43	12.420%	$173.6102	$173.61	$173.60	$173.60
Purchase #4	$156.78	4.736%	$164.2051	$164.21	$164.20	$164.20
Purchase #5	$146.61	5.361%	$154.4698	$154.47	$154.45	$154.50
Purchase #6	$142.82	10.679%	$158.0717	$158.07	$158.05	$158.10
Purchase #7	$121.38	4.640%	$127.012	$127.01	$127.00	$127.00
7 purchase totals =	$1,016.98		$1,105.2139	$1,105.21	$1,105.15	$1,105.20