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	$149.39	10.218%	$164.6547	$164.65	$164.65	$164.70
Purchase #2	$146.78	4.679%	$153.6478	$153.65	$153.65	$153.60
Purchase #3	$81.94	9.221%	$89.4957	$89.50	$89.50	$89.50
Purchase #4	$80.81	3.605%	$83.7232	$83.72	$83.70	$83.70
Purchase #5	$166.89	7.463%	$179.345	$179.35	$179.35	$179.30
Purchase #6	$158.99	3.772%	$164.9871	$164.99	$165.00	$165.00
Purchase #7	$112.35	12.552%	$126.4522	$126.45	$126.45	$126.50
7 purchase totals =	$897.15		$962.3057	$962.31	$962.30	$962.30