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	$144.32	11.341%	$160.6873	$160.69	$160.70	$160.70
Purchase #2	$115.71	11.191%	$128.6591	$128.66	$128.65	$128.70
Purchase #3	$165.82	12.482%	$186.5177	$186.52	$186.50	$186.50
Purchase #4	$145.46	6.720%	$155.2349	$155.23	$155.25	$155.20
Purchase #5	$41.57	4.852%	$43.587	$43.59	$43.60	$43.60
Purchase #6	$224.96	4.811%	$235.7828	$235.78	$235.80	$235.80
Purchase #7	$241.30	8.676%	$262.2352	$262.24	$262.25	$262.20
7 purchase totals =	$1,079.14		$1,172.7040	$1,172.71	$1,172.75	$1,172.70