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	$96.32	12.547%	$108.4053	$108.41	$108.40	$108.40
Purchase #2	$200.89	10.434%	$221.8509	$221.85	$221.85	$221.90
Purchase #3	$78.36	10.291%	$86.424	$86.42	$86.40	$86.40
Purchase #4	$205.40	8.213%	$222.2695	$222.27	$222.25	$222.30
Purchase #5	$43.32	7.572%	$46.6002	$46.60	$46.60	$46.60
Purchase #6	$231.43	9.616%	$253.6843	$253.68	$253.70	$253.70
Purchase #7	$74.25	8.204%	$80.3415	$80.34	$80.35	$80.30
7 purchase totals =	$929.97		$1,019.5757	$1,019.57	$1,019.55	$1,019.60