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	$206.92	4.136%	$215.4782	$215.48	$215.50	$215.50
Purchase #2	$242.68	3.205%	$250.4579	$250.46	$250.45	$250.50
Purchase #3	$111.84	10.164%	$123.2074	$123.21	$123.20	$123.20
Purchase #4	$116.38	9.767%	$127.7468	$127.75	$127.75	$127.70
Purchase #5	$223.43	3.305%	$230.8144	$230.81	$230.80	$230.80
Purchase #6	$142.98	10.687%	$158.2603	$158.26	$158.25	$158.30
Purchase #7	$241.66	11.361%	$269.115	$269.12	$269.10	$269.10
7 purchase totals =	$1,285.89		$1,375.0800	$1,375.09	$1,375.05	$1,375.10