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	$129.99	11.456%	$144.8817	$144.88	$144.90	$144.90
Purchase #2	$74.78	3.592%	$77.4661	$77.47	$77.45	$77.50
Purchase #3	$217.81	10.304%	$240.2531	$240.25	$240.25	$240.30
Purchase #4	$246.49	4.190%	$256.8179	$256.82	$256.80	$256.80
Purchase #5	$242.39	4.166%	$252.488	$252.49	$252.50	$252.50
Purchase #6	$11.64	10.727%	$12.8886	$12.89	$12.90	$12.90
Purchase #7	$160.76	10.485%	$177.6157	$177.62	$177.60	$177.60
7 purchase totals =	$1,083.86		$1,162.4111	$1,162.42	$1,162.40	$1,162.50