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	$59.85	10.369%	$66.0558	$66.06	$66.05	$66.10
Purchase #2	$129.51	7.621%	$139.38	$139.38	$139.40	$139.40
Purchase #3	$155.45	12.729%	$175.2372	$175.24	$175.25	$175.20
Purchase #4	$49.53	8.659%	$53.8188	$53.82	$53.80	$53.80
Purchase #5	$18.39	4.799%	$19.2725	$19.27	$19.25	$19.30
Purchase #6	$115.96	6.664%	$123.6876	$123.69	$123.70	$123.70
Purchase #7	$97.73	7.398%	$104.9601	$104.96	$104.95	$105.00
7 purchase totals =	$626.42		$682.4120	$682.42	$682.40	$682.50