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	$205.78	11.779%	$230.0188	$230.02	$230.00	$230.00
Purchase #2	$104.31	11.548%	$116.3557	$116.36	$116.35	$116.40
Purchase #3	$137.27	12.486%	$154.4095	$154.41	$154.40	$154.40
Purchase #4	$116.89	9.831%	$128.3815	$128.38	$128.40	$128.40
Purchase #5	$70.38	10.839%	$78.0085	$78.01	$78.00	$78.00
Purchase #6	$108.65	3.228%	$112.1572	$112.16	$112.15	$112.20
Purchase #7	$172.68	8.761%	$187.8085	$187.81	$187.80	$187.80
7 purchase totals =	$915.96		$1,007.1397	$1,007.15	$1,007.10	$1,007.20