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	$242.68	5.153%	$255.1853	$255.19	$255.20	$255.20
Purchase #2	$80.66	10.373%	$89.0269	$89.03	$89.05	$89.00
Purchase #3	$160.79	3.532%	$166.4691	$166.47	$166.45	$166.50
Purchase #4	$243.46	9.401%	$266.3477	$266.35	$266.35	$266.30
Purchase #5	$42.86	12.833%	$48.3602	$48.36	$48.35	$48.40
Purchase #6	$116.40	9.111%	$127.0052	$127.01	$127.00	$127.00
Purchase #7	$220.38	9.735%	$241.834	$241.83	$241.85	$241.80
7 purchase totals =	$1,107.23		$1,194.2284	$1,194.24	$1,194.25	$1,194.20