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	$94.62	3.411%	$97.8475	$97.85	$97.85	$97.80
Purchase #2	$167.53	9.749%	$183.8625	$183.86	$183.85	$183.90
Purchase #3	$20.60	6.256%	$21.8887	$21.89	$21.90	$21.90
Purchase #4	$29.48	9.825%	$32.3764	$32.38	$32.40	$32.40
Purchase #5	$188.36	5.648%	$198.9986	$199.00	$199.00	$199.00
Purchase #6	$99.87	11.212%	$111.0674	$111.07	$111.05	$111.10
Purchase #7	$104.27	12.671%	$117.4821	$117.48	$117.50	$117.50
7 purchase totals =	$704.73		$763.5232	$763.53	$763.55	$763.60