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	$87.60	11.581%	$97.745	$97.75	$97.75	$97.70
Purchase #2	$41.45	10.145%	$45.6551	$45.66	$45.65	$45.70
Purchase #3	$19.32	8.570%	$20.9757	$20.98	$21.00	$21.00
Purchase #4	$199.75	7.429%	$214.5894	$214.59	$214.60	$214.60
Purchase #5	$54.31	9.225%	$59.3201	$59.32	$59.30	$59.30
Purchase #6	$59.87	3.379%	$61.893	$61.89	$61.90	$61.90
Purchase #7	$85.72	12.779%	$96.6742	$96.67	$96.65	$96.70
7 purchase totals =	$548.02		$596.8525	$596.86	$596.85	$596.90