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	$75.34	9.723%	$82.6653	$82.67	$82.65	$82.70
Purchase #2	$29.83	9.420%	$32.64	$32.64	$32.65	$32.60
Purchase #3	$79.75	4.168%	$83.074	$83.07	$83.05	$83.10
Purchase #4	$16.77	13.474%	$19.0296	$19.03	$19.05	$19.00
Purchase #5	$27.38	8.393%	$29.678	$29.68	$29.70	$29.70
Purchase #6	$95.95	10.557%	$106.0794	$106.08	$106.10	$106.10
Purchase #7	$89.54	11.300%	$99.658	$99.66	$99.65	$99.70
7 purchase totals =	$414.56		$452.8243	$452.83	$452.85	$452.90