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	$184.89	11.159%	$205.5219	$205.52	$205.50	$205.50
Purchase #2	$113.64	8.329%	$123.1051	$123.11	$123.10	$123.10
Purchase #3	$44.71	4.377%	$46.667	$46.67	$46.65	$46.70
Purchase #4	$49.68	13.564%	$56.4186	$56.42	$56.40	$56.40
Purchase #5	$51.27	7.704%	$55.2198	$55.22	$55.20	$55.20
Purchase #6	$111.59	10.781%	$123.6205	$123.62	$123.60	$123.60
Purchase #7	$203.49	3.599%	$210.8136	$210.81	$210.80	$210.80
7 purchase totals =	$759.27		$821.3665	$821.37	$821.25	$821.30