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	$143.55	12.458%	$161.4335	$161.43	$161.45	$161.40
Purchase #2	$245.55	3.864%	$255.0381	$255.04	$255.05	$255.00
Purchase #3	$100.27	3.855%	$104.1354	$104.14	$104.15	$104.10
Purchase #4	$18.65	4.387%	$19.4682	$19.47	$19.45	$19.50
Purchase #5	$71.50	13.759%	$81.3377	$81.34	$81.35	$81.30
Purchase #6	$131.92	9.412%	$144.3363	$144.34	$144.35	$144.30
Purchase #7	$243.41	9.495%	$266.5218	$266.52	$266.50	$266.50
7 purchase totals =	$954.85		$1,032.2710	$1,032.28	$1,032.30	$1,032.10