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	$188.28	7.816%	$202.996	$203.00	$203.00	$203.00
Purchase #2	$14.70	5.456%	$15.502	$15.50	$15.50	$15.50
Purchase #3	$217.99	4.802%	$228.4579	$228.46	$228.45	$228.50
Purchase #4	$113.77	3.798%	$118.091	$118.09	$118.10	$118.10
Purchase #5	$76.94	11.175%	$85.538	$85.54	$85.55	$85.50
Purchase #6	$224.76	4.859%	$235.6811	$235.68	$235.70	$235.70
Purchase #7	$100.73	10.808%	$111.6169	$111.62	$111.60	$111.60
7 purchase totals =	$937.17		$997.8829	$997.89	$997.90	$997.90