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	$198.32	12.264%	$222.642	$222.64	$222.65	$222.60
Purchase #2	$47.90	4.660%	$50.1321	$50.13	$50.15	$50.10
Purchase #3	$102.44	8.432%	$111.0777	$111.08	$111.10	$111.10
Purchase #4	$73.98	10.474%	$81.7287	$81.73	$81.75	$81.70
Purchase #5	$96.96	3.162%	$100.0259	$100.03	$100.05	$100.00
Purchase #6	$176.95	11.149%	$196.6782	$196.68	$196.70	$196.70
Purchase #7	$223.55	3.143%	$230.5762	$230.58	$230.60	$230.60
7 purchase totals =	$920.10		$992.8608	$992.87	$993.00	$992.80