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	$66.69	8.697%	$72.49	$72.49	$72.50	$72.50
Purchase #2	$141.57	9.835%	$155.4934	$155.49	$155.50	$155.50
Purchase #3	$233.74	7.830%	$252.0418	$252.04	$252.05	$252.00
Purchase #4	$92.94	13.488%	$105.4757	$105.48	$105.50	$105.50
Purchase #5	$23.38	7.601%	$25.1571	$25.16	$25.15	$25.20
Purchase #6	$226.61	10.858%	$251.2153	$251.22	$251.20	$251.20
Purchase #7	$248.30	3.208%	$256.2655	$256.27	$256.25	$256.30
7 purchase totals =	$1,033.23		$1,118.1388	$1,118.15	$1,118.15	$1,118.20