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	$216.33	3.349%	$223.5749	$223.57	$223.55	$223.60
Purchase #2	$130.73	10.685%	$144.6985	$144.70	$144.70	$144.70
Purchase #3	$49.68	13.301%	$56.2879	$56.29	$56.30	$56.30
Purchase #4	$47.93	6.441%	$51.0172	$51.02	$51.00	$51.00
Purchase #5	$54.86	13.534%	$62.2848	$62.28	$62.30	$62.30
Purchase #6	$112.26	12.464%	$126.2521	$126.25	$126.25	$126.30
Purchase #7	$102.42	8.766%	$111.3981	$111.40	$111.40	$111.40
7 purchase totals =	$714.21		$775.5135	$775.51	$775.50	$775.60