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	$145.49	13.766%	$165.5182	$165.52	$165.50	$165.50
Purchase #2	$65.33	6.568%	$69.6209	$69.62	$69.60	$69.60
Purchase #3	$33.89	13.289%	$38.3936	$38.39	$38.40	$38.40
Purchase #4	$36.88	3.656%	$38.2283	$38.23	$38.25	$38.20
Purchase #5	$76.61	7.338%	$82.2316	$82.23	$82.25	$82.20
Purchase #6	$149.86	5.312%	$157.8206	$157.82	$157.80	$157.80
Purchase #7	$132.92	8.232%	$143.862	$143.86	$143.85	$143.90
7 purchase totals =	$640.98		$695.6752	$695.67	$695.65	$695.60