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	$151.92	8.636%	$165.0398	$165.04	$165.05	$165.00
Purchase #2	$99.49	5.606%	$105.0674	$105.07	$105.05	$105.10
Purchase #3	$121.77	13.315%	$137.9837	$137.98	$138.00	$138.00
Purchase #4	$97.28	6.428%	$103.5332	$103.53	$103.55	$103.50
Purchase #5	$213.90	12.617%	$240.8878	$240.89	$240.90	$240.90
Purchase #6	$169.63	12.176%	$190.2841	$190.28	$190.30	$190.30
Purchase #7	$157.97	11.213%	$175.6832	$175.68	$175.70	$175.70
7 purchase totals =	$1,011.96		$1,118.4792	$1,118.47	$1,118.55	$1,118.50