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	$183.51	9.236%	$200.459	$200.46	$200.45	$200.50
Purchase #2	$84.43	6.726%	$90.1088	$90.11	$90.10	$90.10
Purchase #3	$165.87	10.609%	$183.4671	$183.47	$183.45	$183.50
Purchase #4	$115.60	11.352%	$128.7229	$128.72	$128.70	$128.70
Purchase #5	$11.98	9.166%	$13.0781	$13.08	$13.10	$13.10
Purchase #6	$60.37	12.550%	$67.9464	$67.95	$67.95	$67.90
Purchase #7	$73.27	6.472%	$78.012	$78.01	$78.00	$78.00
7 purchase totals =	$695.03		$761.7943	$761.80	$761.75	$761.80