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	$101.67	9.319%	$111.1446	$111.14	$111.15	$111.10
Purchase #2	$6.88	6.379%	$7.3189	$7.32	$7.30	$7.30
Purchase #3	$248.39	13.842%	$282.7721	$282.77	$282.75	$282.80
Purchase #4	$41.54	11.295%	$46.2319	$46.23	$46.25	$46.20
Purchase #5	$154.48	3.327%	$159.6195	$159.62	$159.60	$159.60
Purchase #6	$10.99	8.328%	$11.9052	$11.91	$11.90	$11.90
Purchase #7	$150.88	6.325%	$160.4232	$160.42	$160.40	$160.40
7 purchase totals =	$714.83		$779.4154	$779.41	$779.35	$779.30