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	$111.64	4.715%	$116.9038	$116.90	$116.90	$116.90
Purchase #2	$77.26	6.686%	$82.4256	$82.43	$82.45	$82.40
Purchase #3	$49.79	8.719%	$54.1312	$54.13	$54.15	$54.10
Purchase #4	$203.68	9.340%	$222.7037	$222.70	$222.70	$222.70
Purchase #5	$114.61	3.332%	$118.4288	$118.43	$118.45	$118.40
Purchase #6	$56.97	10.247%	$62.8077	$62.81	$62.80	$62.80
Purchase #7	$195.60	12.712%	$220.4647	$220.46	$220.45	$220.50
7 purchase totals =	$809.55		$877.8655	$877.86	$877.90	$877.80