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	$91.61	8.526%	$99.4207	$99.42	$99.40	$99.40
Purchase #2	$137.87	4.318%	$143.8232	$143.82	$143.80	$143.80
Purchase #3	$59.44	8.348%	$64.4021	$64.40	$64.40	$64.40
Purchase #4	$144.87	12.393%	$162.8237	$162.82	$162.80	$162.80
Purchase #5	$145.25	10.350%	$160.2834	$160.28	$160.30	$160.30
Purchase #6	$241.38	8.697%	$262.3728	$262.37	$262.35	$262.40
Purchase #7	$173.82	11.423%	$193.6755	$193.68	$193.70	$193.70
7 purchase totals =	$994.24		$1,086.8014	$1,086.79	$1,086.75	$1,086.80