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	$112.78	13.103%	$127.5576	$127.56	$127.55	$127.60
Purchase #2	$116.96	12.870%	$132.0128	$132.01	$132.00	$132.00
Purchase #3	$100.66	11.320%	$112.0547	$112.05	$112.05	$112.10
Purchase #4	$140.45	10.711%	$155.4936	$155.49	$155.50	$155.50
Purchase #5	$127.35	12.449%	$143.2038	$143.20	$143.20	$143.20
Purchase #6	$115.32	3.111%	$118.9076	$118.91	$118.90	$118.90
Purchase #7	$190.62	7.646%	$205.1948	$205.19	$205.20	$205.20
7 purchase totals =	$904.14		$994.4249	$994.41	$994.40	$994.50