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	$94.87	13.660%	$107.8292	$107.83	$107.85	$107.80
Purchase #2	$61.28	4.727%	$64.1767	$64.18	$64.20	$64.20
Purchase #3	$99.85	3.338%	$103.183	$103.18	$103.20	$103.20
Purchase #4	$69.92	5.788%	$73.967	$73.97	$73.95	$74.00
Purchase #5	$102.57	9.127%	$111.9316	$111.93	$111.95	$111.90
Purchase #6	$101.61	9.335%	$111.0953	$111.10	$111.10	$111.10
Purchase #7	$126.71	10.752%	$140.3339	$140.33	$140.35	$140.30
7 purchase totals =	$656.81		$712.5167	$712.52	$712.60	$712.50