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	$56.61	12.369%	$63.6121	$63.61	$63.60	$63.60
Purchase #2	$110.28	3.528%	$114.1707	$114.17	$114.15	$114.20
Purchase #3	$144.28	12.137%	$161.7913	$161.79	$161.80	$161.80
Purchase #4	$236.89	9.211%	$258.7099	$258.71	$258.70	$258.70
Purchase #5	$102.71	13.537%	$116.6139	$116.61	$116.60	$116.60
Purchase #6	$88.43	13.215%	$100.116	$100.12	$100.10	$100.10
Purchase #7	$243.61	4.505%	$254.5846	$254.58	$254.60	$254.60
7 purchase totals =	$982.81		$1,069.5985	$1,069.59	$1,069.55	$1,069.60