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	$90.58	10.331%	$99.9378	$99.94	$99.95	$99.90
Purchase #2	$38.35	4.652%	$40.134	$40.13	$40.15	$40.10
Purchase #3	$33.96	13.801%	$38.6468	$38.65	$38.65	$38.60
Purchase #4	$244.36	9.629%	$267.8894	$267.89	$267.90	$267.90
Purchase #5	$144.55	13.165%	$163.58	$163.58	$163.60	$163.60
Purchase #6	$103.56	12.467%	$116.4708	$116.47	$116.45	$116.50
Purchase #7	$242.27	5.647%	$255.951	$255.95	$255.95	$256.00
7 purchase totals =	$897.63		$982.6098	$982.61	$982.65	$982.60