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	$183.80	6.724%	$196.1587	$196.16	$196.15	$196.20
Purchase #2	$184.26	8.773%	$200.4251	$200.43	$200.45	$200.40
Purchase #3	$51.80	5.415%	$54.605	$54.61	$54.60	$54.60
Purchase #4	$78.47	9.304%	$85.7708	$85.77	$85.75	$85.80
Purchase #5	$98.37	6.770%	$105.0296	$105.03	$105.05	$105.00
Purchase #6	$139.28	4.827%	$146.003	$146.00	$146.00	$146.00
Purchase #7	$160.37	13.380%	$181.8275	$181.83	$181.85	$181.80
7 purchase totals =	$896.35		$969.8197	$969.83	$969.85	$969.80