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	$103.50	8.615%	$112.4165	$112.42	$112.40	$112.40
Purchase #2	$98.28	13.557%	$111.6038	$111.60	$111.60	$111.60
Purchase #3	$40.35	4.716%	$42.2529	$42.25	$42.25	$42.30
Purchase #4	$88.61	13.504%	$100.5759	$100.58	$100.60	$100.60
Purchase #5	$250.25	3.412%	$258.7885	$258.79	$258.80	$258.80
Purchase #6	$220.92	6.719%	$235.7636	$235.76	$235.75	$235.80
Purchase #7	$250.58	11.687%	$279.8653	$279.87	$279.85	$279.90
7 purchase totals =	$1,052.49		$1,141.2665	$1,141.27	$1,141.25	$1,141.40