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	$97.89	8.210%	$105.9268	$105.93	$105.95	$105.90
Purchase #2	$41.27	7.528%	$44.3768	$44.38	$44.40	$44.40
Purchase #3	$51.90	5.837%	$54.9294	$54.93	$54.95	$54.90
Purchase #4	$52.91	9.508%	$57.9407	$57.94	$57.95	$57.90
Purchase #5	$95.41	11.663%	$106.5377	$106.54	$106.55	$106.50
Purchase #6	$12.83	6.688%	$13.6881	$13.69	$13.70	$13.70
Purchase #7	$70.40	10.624%	$77.8793	$77.88	$77.90	$77.90
7 purchase totals =	$422.61		$461.2788	$461.29	$461.40	$461.20