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	$139.65	4.532%	$145.9789	$145.98	$146.00	$146.00
Purchase #2	$122.63	7.531%	$131.8653	$131.87	$131.85	$131.90
Purchase #3	$190.71	5.178%	$200.585	$200.59	$200.60	$200.60
Purchase #4	$166.61	4.359%	$173.8725	$173.87	$173.85	$173.90
Purchase #5	$230.27	13.813%	$262.0772	$262.08	$262.10	$262.10
Purchase #6	$78.37	6.290%	$83.2995	$83.30	$83.30	$83.30
Purchase #7	$22.99	8.853%	$25.0253	$25.03	$25.05	$25.00
7 purchase totals =	$951.23		$1,022.7037	$1,022.72	$1,022.75	$1,022.80