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	$9.94	10.448%	$10.9785	$10.98	$11.00	$11.00
Purchase #2	$209.44	5.809%	$221.6064	$221.61	$221.60	$221.60
Purchase #3	$22.90	8.380%	$24.819	$24.82	$24.80	$24.80
Purchase #4	$150.46	4.197%	$156.7748	$156.77	$156.75	$156.80
Purchase #5	$78.41	13.538%	$89.0251	$89.03	$89.05	$89.00
Purchase #6	$10.37	12.108%	$11.6256	$11.63	$11.65	$11.60
Purchase #7	$107.72	3.822%	$111.8371	$111.84	$111.85	$111.80
7 purchase totals =	$589.24		$626.6665	$626.68	$626.70	$626.60