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	$105.75	11.192%	$117.5855	$117.59	$117.60	$117.60
Purchase #2	$218.35	6.434%	$232.3986	$232.40	$232.40	$232.40
Purchase #3	$158.46	13.106%	$179.2278	$179.23	$179.25	$179.20
Purchase #4	$111.64	4.702%	$116.8893	$116.89	$116.90	$116.90
Purchase #5	$108.90	6.195%	$115.6464	$115.65	$115.65	$115.60
Purchase #6	$53.69	13.509%	$60.943	$60.94	$60.95	$60.90
Purchase #7	$160.45	12.108%	$179.8773	$179.88	$179.90	$179.90
7 purchase totals =	$917.24		$1,002.5679	$1,002.58	$1,002.65	$1,002.50