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	$119.67	5.704%	$126.496	$126.50	$126.50	$126.50
Purchase #2	$73.47	6.559%	$78.2889	$78.29	$78.30	$78.30
Purchase #3	$10.76	13.398%	$12.2016	$12.20	$12.20	$12.20
Purchase #4	$233.94	13.823%	$266.2775	$266.28	$266.30	$266.30
Purchase #5	$70.40	10.702%	$77.9342	$77.93	$77.95	$77.90
Purchase #6	$100.75	10.759%	$111.5897	$111.59	$111.60	$111.60
Purchase #7	$227.34	8.782%	$247.305	$247.31	$247.30	$247.30
7 purchase totals =	$836.33		$920.0929	$920.10	$920.15	$920.10