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	$116.32	9.508%	$127.3797	$127.38	$127.40	$127.40
Purchase #2	$122.56	3.807%	$127.2259	$127.23	$127.25	$127.20
Purchase #3	$171.50	9.719%	$188.1681	$188.17	$188.15	$188.20
Purchase #4	$186.70	3.139%	$192.5605	$192.56	$192.55	$192.60
Purchase #5	$175.86	4.559%	$183.8775	$183.88	$183.90	$183.90
Purchase #6	$68.54	10.692%	$75.8683	$75.87	$75.85	$75.90
Purchase #7	$56.75	13.794%	$64.5781	$64.58	$64.60	$64.60
7 purchase totals =	$898.23		$959.6581	$959.67	$959.70	$959.80