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	$222.35	13.121%	$251.5245	$251.52	$251.50	$251.50
Purchase #2	$230.72	10.686%	$255.3747	$255.37	$255.35	$255.40
Purchase #3	$208.51	6.867%	$222.8284	$222.83	$222.85	$222.80
Purchase #4	$226.63	10.505%	$250.4375	$250.44	$250.45	$250.40
Purchase #5	$93.35	4.126%	$97.2016	$97.20	$97.20	$97.20
Purchase #6	$14.99	12.795%	$16.908	$16.91	$16.90	$16.90
Purchase #7	$39.30	7.696%	$42.3245	$42.32	$42.30	$42.30
7 purchase totals =	$1,035.85		$1,136.5992	$1,136.59	$1,136.55	$1,136.50