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	$173.52	3.487%	$179.5706	$179.57	$179.55	$179.60
Purchase #2	$193.29	5.826%	$204.5511	$204.55	$204.55	$204.60
Purchase #3	$88.25	12.599%	$99.3686	$99.37	$99.35	$99.40
Purchase #4	$120.76	5.650%	$127.5829	$127.58	$127.60	$127.60
Purchase #5	$234.82	4.536%	$245.4714	$245.47	$245.45	$245.50
Purchase #6	$238.88	10.735%	$264.5238	$264.52	$264.50	$264.50
Purchase #7	$108.80	7.365%	$116.8131	$116.81	$116.80	$116.80
7 purchase totals =	$1,158.32		$1,237.8815	$1,237.87	$1,237.80	$1,238.00