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	$207.52	13.840%	$236.2408	$236.24	$236.25	$236.20
Purchase #2	$112.94	9.145%	$123.2684	$123.27	$123.25	$123.30
Purchase #3	$60.53	8.137%	$65.4553	$65.46	$65.45	$65.50
Purchase #4	$188.64	12.467%	$212.1577	$212.16	$212.15	$212.20
Purchase #5	$184.31	3.452%	$190.6724	$190.67	$190.65	$190.70
Purchase #6	$102.61	13.396%	$116.3556	$116.36	$116.35	$116.40
Purchase #7	$103.32	4.103%	$107.5592	$107.56	$107.55	$107.60
7 purchase totals =	$959.87		$1,051.7094	$1,051.72	$1,051.65	$1,051.90