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	$68.31	6.682%	$72.8745	$72.87	$72.85	$72.90
Purchase #2	$12.66	6.377%	$13.4673	$13.47	$13.45	$13.50
Purchase #3	$162.40	6.678%	$173.2451	$173.25	$173.25	$173.20
Purchase #4	$18.65	5.650%	$19.7037	$19.70	$19.70	$19.70
Purchase #5	$58.76	11.487%	$65.5098	$65.51	$65.50	$65.50
Purchase #6	$95.91	7.404%	$103.0112	$103.01	$103.00	$103.00
Purchase #7	$146.56	6.178%	$155.6145	$155.61	$155.60	$155.60
7 purchase totals =	$563.25		$603.4261	$603.42	$603.35	$603.40