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	$54.75	9.313%	$59.8489	$59.85	$59.85	$59.80
Purchase #2	$32.45	10.519%	$35.8634	$35.86	$35.85	$35.90
Purchase #3	$28.48	6.340%	$30.2856	$30.29	$30.30	$30.30
Purchase #4	$132.59	8.407%	$143.7368	$143.74	$143.75	$143.70
Purchase #5	$191.75	13.622%	$217.8702	$217.87	$217.85	$217.90
Purchase #6	$19.62	10.535%	$21.687	$21.69	$21.70	$21.70
Purchase #7	$196.78	4.572%	$205.7768	$205.78	$205.80	$205.80
7 purchase totals =	$656.42		$715.0687	$715.08	$715.10	$715.10