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	$217.47	13.263%	$246.313	$246.31	$246.30	$246.30
Purchase #2	$46.25	4.711%	$48.4288	$48.43	$48.45	$48.40
Purchase #3	$163.85	3.164%	$169.0342	$169.03	$169.05	$169.00
Purchase #4	$91.51	13.275%	$103.658	$103.66	$103.65	$103.70
Purchase #5	$132.40	9.128%	$144.4855	$144.49	$144.50	$144.50
Purchase #6	$12.31	4.221%	$12.8296	$12.83	$12.85	$12.80
Purchase #7	$140.75	10.524%	$155.5625	$155.56	$155.55	$155.60
7 purchase totals =	$804.54		$880.3116	$880.31	$880.35	$880.30