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	$9.46	11.619%	$10.5592	$10.56	$10.55	$10.60
Purchase #2	$189.71	9.803%	$208.3073	$208.31	$208.30	$208.30
Purchase #3	$181.50	9.788%	$199.2652	$199.27	$199.25	$199.30
Purchase #4	$103.34	8.159%	$111.7715	$111.77	$111.75	$111.80
Purchase #5	$18.82	8.392%	$20.3994	$20.40	$20.40	$20.40
Purchase #6	$225.38	10.202%	$248.3733	$248.37	$248.35	$248.40
Purchase #7	$236.32	13.191%	$267.493	$267.49	$267.50	$267.50
7 purchase totals =	$964.53		$1,066.1689	$1,066.17	$1,066.10	$1,066.30