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	$40.97	13.797%	$46.6226	$46.62	$46.60	$46.60
Purchase #2	$143.99	4.561%	$150.5574	$150.56	$150.55	$150.60
Purchase #3	$56.31	11.272%	$62.6573	$62.66	$62.65	$62.70
Purchase #4	$61.95	7.650%	$66.6892	$66.69	$66.70	$66.70
Purchase #5	$235.30	8.527%	$255.364	$255.36	$255.35	$255.40
Purchase #6	$161.43	3.333%	$166.8105	$166.81	$166.80	$166.80
Purchase #7	$90.27	13.488%	$102.4456	$102.45	$102.45	$102.40
7 purchase totals =	$790.22		$851.1466	$851.15	$851.10	$851.20