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	$41.28	5.487%	$43.545	$43.55	$43.55	$43.50
Purchase #2	$139.39	4.505%	$145.6695	$145.67	$145.65	$145.70
Purchase #3	$248.31	6.386%	$264.1671	$264.17	$264.15	$264.20
Purchase #4	$158.32	9.301%	$173.0453	$173.05	$173.05	$173.00
Purchase #5	$21.48	13.561%	$24.3929	$24.39	$24.40	$24.40
Purchase #6	$237.43	7.459%	$255.1399	$255.14	$255.15	$255.10
Purchase #7	$81.29	7.583%	$87.4542	$87.45	$87.45	$87.50
7 purchase totals =	$927.50		$993.4139	$993.42	$993.40	$993.40