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	$133.96	12.787%	$151.0895	$151.09	$151.10	$151.10
Purchase #2	$132.91	3.514%	$137.5805	$137.58	$137.60	$137.60
Purchase #3	$38.31	4.695%	$40.1087	$40.11	$40.10	$40.10
Purchase #4	$69.29	12.699%	$78.0891	$78.09	$78.10	$78.10
Purchase #5	$139.31	4.149%	$145.09	$145.09	$145.10	$145.10
Purchase #6	$105.74	9.721%	$116.019	$116.02	$116.00	$116.00
Purchase #7	$10.71	6.855%	$11.4442	$11.44	$11.45	$11.40
7 purchase totals =	$630.23		$679.4210	$679.42	$679.45	$679.40