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	$151.76	6.677%	$161.893	$161.89	$161.90	$161.90
Purchase #2	$47.51	10.233%	$52.3717	$52.37	$52.35	$52.40
Purchase #3	$101.82	9.177%	$111.164	$111.16	$111.15	$111.20
Purchase #4	$231.49	4.683%	$242.3307	$242.33	$242.35	$242.30
Purchase #5	$181.36	5.307%	$190.9848	$190.98	$191.00	$191.00
Purchase #6	$20.97	3.569%	$21.7184	$21.72	$21.70	$21.70
Purchase #7	$204.45	8.441%	$221.7076	$221.71	$221.70	$221.70
7 purchase totals =	$939.36		$1,002.1702	$1,002.16	$1,002.15	$1,002.20