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	$66.25	8.746%	$72.0442	$72.04	$72.05	$72.00
Purchase #2	$64.27	9.456%	$70.3474	$70.35	$70.35	$70.30
Purchase #3	$58.76	5.273%	$61.8584	$61.86	$61.85	$61.90
Purchase #4	$127.57	9.842%	$140.1254	$140.13	$140.15	$140.10
Purchase #5	$224.41	10.749%	$248.5318	$248.53	$248.55	$248.50
Purchase #6	$159.99	6.671%	$170.6629	$170.66	$170.65	$170.70
Purchase #7	$56.69	4.490%	$59.2354	$59.24	$59.25	$59.20
7 purchase totals =	$757.94		$822.8055	$822.81	$822.85	$822.70