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	$130.70	11.361%	$145.5488	$145.55	$145.55	$145.50
Purchase #2	$227.72	3.392%	$235.4443	$235.44	$235.45	$235.40
Purchase #3	$217.49	13.285%	$246.3835	$246.38	$246.40	$246.40
Purchase #4	$154.80	4.859%	$162.3217	$162.32	$162.30	$162.30
Purchase #5	$118.94	3.768%	$123.4217	$123.42	$123.40	$123.40
Purchase #6	$36.59	11.550%	$40.8161	$40.82	$40.80	$40.80
Purchase #7	$130.44	10.563%	$144.2184	$144.22	$144.20	$144.20
7 purchase totals =	$1,016.68		$1,098.1545	$1,098.15	$1,098.10	$1,098.00