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	$119.28	12.835%	$134.5896	$134.59	$134.60	$134.60
Purchase #2	$106.80	4.491%	$111.5964	$111.60	$111.60	$111.60
Purchase #3	$8.86	10.683%	$9.8065	$9.81	$9.80	$9.80
Purchase #4	$62.69	6.305%	$66.6426	$66.64	$66.65	$66.60
Purchase #5	$98.71	4.426%	$103.0789	$103.08	$103.10	$103.10
Purchase #6	$246.94	11.149%	$274.4713	$274.47	$274.45	$274.50
Purchase #7	$232.82	4.120%	$242.4122	$242.41	$242.40	$242.40
7 purchase totals =	$876.10		$942.5975	$942.60	$942.60	$942.60