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	$105.32	4.439%	$109.9952	$110.00	$110.00	$110.00
Purchase #2	$103.99	10.526%	$114.936	$114.94	$114.95	$114.90
Purchase #3	$54.72	8.492%	$59.3668	$59.37	$59.35	$59.40
Purchase #4	$233.38	11.592%	$260.4334	$260.43	$260.45	$260.40
Purchase #5	$113.77	9.205%	$124.2425	$124.24	$124.25	$124.20
Purchase #6	$48.39	11.476%	$53.9432	$53.94	$53.95	$53.90
Purchase #7	$132.25	9.719%	$145.1034	$145.10	$145.10	$145.10
7 purchase totals =	$791.82		$868.0205	$868.02	$868.05	$867.90