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	$240.38	8.125%	$259.9109	$259.91	$259.90	$259.90
Purchase #2	$53.63	3.653%	$55.5891	$55.59	$55.60	$55.60
Purchase #3	$197.90	10.371%	$218.4242	$218.42	$218.40	$218.40
Purchase #4	$34.45	5.602%	$36.3799	$36.38	$36.40	$36.40
Purchase #5	$213.66	4.492%	$223.2576	$223.26	$223.25	$223.30
Purchase #6	$214.64	4.309%	$223.8888	$223.89	$223.90	$223.90
Purchase #7	$196.63	13.436%	$223.0492	$223.05	$223.05	$223.00
7 purchase totals =	$1,151.29		$1,240.4997	$1,240.50	$1,240.50	$1,240.50