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	$217.50	7.577%	$233.98	$233.98	$234.00	$234.00
Purchase #2	$127.72	8.264%	$138.2748	$138.27	$138.25	$138.30
Purchase #3	$50.84	9.714%	$55.7786	$55.78	$55.80	$55.80
Purchase #4	$170.45	6.246%	$181.0963	$181.10	$181.10	$181.10
Purchase #5	$198.94	5.859%	$210.5959	$210.60	$210.60	$210.60
Purchase #6	$83.69	3.242%	$86.4032	$86.40	$86.40	$86.40
Purchase #7	$119.88	6.316%	$127.4516	$127.45	$127.45	$127.50
7 purchase totals =	$969.02		$1,033.5804	$1,033.58	$1,033.60	$1,033.70