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	$81.75	7.181%	$87.6205	$87.62	$87.60	$87.60
Purchase #2	$219.92	5.444%	$231.8924	$231.89	$231.90	$231.90
Purchase #3	$8.96	5.175%	$9.4237	$9.42	$9.40	$9.40
Purchase #4	$101.66	9.632%	$111.4519	$111.45	$111.45	$111.50
Purchase #5	$107.90	3.439%	$111.6107	$111.61	$111.60	$111.60
Purchase #6	$70.46	9.653%	$77.2615	$77.26	$77.25	$77.30
Purchase #7	$238.89	12.114%	$267.8291	$267.83	$267.85	$267.80
7 purchase totals =	$829.54		$897.0898	$897.08	$897.05	$897.10