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	$162.85	4.171%	$169.6425	$169.64	$169.65	$169.60
Purchase #2	$140.68	6.797%	$150.242	$150.24	$150.25	$150.20
Purchase #3	$91.35	5.139%	$96.0445	$96.04	$96.05	$96.00
Purchase #4	$77.32	8.278%	$83.7205	$83.72	$83.70	$83.70
Purchase #5	$145.61	13.198%	$164.8276	$164.83	$164.85	$164.80
Purchase #6	$12.78	4.756%	$13.3878	$13.39	$13.40	$13.40
Purchase #7	$126.46	8.815%	$137.6074	$137.61	$137.60	$137.60
7 purchase totals =	$757.05		$815.4723	$815.47	$815.50	$815.30