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	$58.69	3.839%	$60.9431	$60.94	$60.95	$60.90
Purchase #2	$94.29	9.257%	$103.0184	$103.02	$103.00	$103.00
Purchase #3	$31.43	6.205%	$33.3802	$33.38	$33.40	$33.40
Purchase #4	$17.84	4.338%	$18.6139	$18.61	$18.60	$18.60
Purchase #5	$150.76	6.827%	$161.0524	$161.05	$161.05	$161.10
Purchase #6	$70.95	10.162%	$78.1599	$78.16	$78.15	$78.20
Purchase #7	$133.59	8.400%	$144.8116	$144.81	$144.80	$144.80
7 purchase totals =	$557.55		$599.9795	$599.97	$599.95	$600.00