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	$87.61	10.312%	$96.6443	$96.64	$96.65	$96.60
Purchase #2	$157.79	4.633%	$165.1004	$165.10	$165.10	$165.10
Purchase #3	$103.69	4.407%	$108.2596	$108.26	$108.25	$108.30
Purchase #4	$143.58	10.148%	$158.1505	$158.15	$158.15	$158.20
Purchase #5	$104.39	7.193%	$111.8988	$111.90	$111.90	$111.90
Purchase #6	$62.52	4.497%	$65.3315	$65.33	$65.35	$65.30
Purchase #7	$200.50	13.737%	$228.0427	$228.04	$228.05	$228.00
7 purchase totals =	$860.08		$933.4278	$933.42	$933.45	$933.40