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	$81.27	5.874%	$86.0438	$86.04	$86.05	$86.00
Purchase #2	$223.40	8.239%	$241.8059	$241.81	$241.80	$241.80
Purchase #3	$143.60	12.347%	$161.3303	$161.33	$161.35	$161.30
Purchase #4	$111.84	13.473%	$126.9082	$126.91	$126.90	$126.90
Purchase #5	$178.43	6.211%	$189.5123	$189.51	$189.50	$189.50
Purchase #6	$138.79	5.388%	$146.268	$146.27	$146.25	$146.30
Purchase #7	$61.30	10.118%	$67.5023	$67.50	$67.50	$67.50
7 purchase totals =	$938.63		$1,019.3708	$1,019.37	$1,019.35	$1,019.30