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	$49.26	13.143%	$55.7342	$55.73	$55.75	$55.70
Purchase #2	$172.36	11.106%	$191.5023	$191.50	$191.50	$191.50
Purchase #3	$70.39	11.722%	$78.6411	$78.64	$78.65	$78.60
Purchase #4	$105.29	8.382%	$114.1154	$114.12	$114.10	$114.10
Purchase #5	$240.77	7.222%	$258.1584	$258.16	$258.15	$258.20
Purchase #6	$123.48	7.436%	$132.662	$132.66	$132.65	$132.70
Purchase #7	$212.81	10.248%	$234.6188	$234.62	$234.60	$234.60
7 purchase totals =	$974.36		$1,065.4322	$1,065.43	$1,065.40	$1,065.40