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	$112.98	9.230%	$123.4081	$123.41	$123.40	$123.40
Purchase #2	$44.27	3.215%	$45.6933	$45.69	$45.70	$45.70
Purchase #3	$246.35	10.276%	$271.6649	$271.66	$271.65	$271.70
Purchase #4	$111.38	13.827%	$126.7805	$126.78	$126.80	$126.80
Purchase #5	$28.52	10.393%	$31.4841	$31.48	$31.50	$31.50
Purchase #6	$139.86	6.585%	$149.0698	$149.07	$149.05	$149.10
Purchase #7	$48.70	11.195%	$54.152	$54.15	$54.15	$54.20
7 purchase totals =	$732.06		$802.2527	$802.24	$802.25	$802.40