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	$164.58	10.444%	$181.7687	$181.77	$181.75	$181.80
Purchase #2	$108.34	4.162%	$112.8491	$112.85	$112.85	$112.80
Purchase #3	$184.63	3.297%	$190.7173	$190.72	$190.70	$190.70
Purchase #4	$54.65	5.379%	$57.5896	$57.59	$57.60	$57.60
Purchase #5	$121.78	13.249%	$137.9146	$137.91	$137.90	$137.90
Purchase #6	$81.54	8.675%	$88.6136	$88.61	$88.60	$88.60
Purchase #7	$15.73	11.517%	$17.5416	$17.54	$17.55	$17.50
7 purchase totals =	$731.25		$786.9945	$786.99	$786.95	$786.90