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	$74.66	4.770%	$78.2213	$78.22	$78.20	$78.20
Purchase #2	$228.64	13.159%	$258.7267	$258.73	$258.75	$258.70
Purchase #3	$148.32	6.756%	$158.3405	$158.34	$158.35	$158.30
Purchase #4	$66.73	7.609%	$71.8075	$71.81	$71.80	$71.80
Purchase #5	$210.74	5.111%	$221.5109	$221.51	$221.50	$221.50
Purchase #6	$207.38	6.867%	$221.6208	$221.62	$221.60	$221.60
Purchase #7	$10.95	10.294%	$12.0772	$12.08	$12.10	$12.10
7 purchase totals =	$947.42		$1,022.3049	$1,022.31	$1,022.30	$1,022.20