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	$144.49	12.852%	$163.0599	$163.06	$163.05	$163.10
Purchase #2	$123.92	12.751%	$139.721	$139.72	$139.70	$139.70
Purchase #3	$145.35	9.450%	$159.0856	$159.09	$159.10	$159.10
Purchase #4	$119.61	6.612%	$127.5186	$127.52	$127.50	$127.50
Purchase #5	$150.83	10.379%	$166.4846	$166.48	$166.50	$166.50
Purchase #6	$135.32	4.285%	$141.1185	$141.12	$141.10	$141.10
Purchase #7	$158.66	7.182%	$170.055	$170.06	$170.05	$170.10
7 purchase totals =	$978.18		$1,067.0432	$1,067.05	$1,067.00	$1,067.10