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	$153.79	5.693%	$162.5453	$162.55	$162.55	$162.50
Purchase #2	$109.72	6.429%	$116.7739	$116.77	$116.75	$116.80
Purchase #3	$50.95	4.131%	$53.0547	$53.05	$53.05	$53.10
Purchase #4	$57.30	10.773%	$63.4729	$63.47	$63.45	$63.50
Purchase #5	$234.60	8.841%	$255.341	$255.34	$255.35	$255.30
Purchase #6	$57.58	6.218%	$61.1603	$61.16	$61.15	$61.20
Purchase #7	$114.49	8.600%	$124.3361	$124.34	$124.35	$124.30
7 purchase totals =	$778.43		$836.6842	$836.68	$836.65	$836.70