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	$59.95	11.492%	$66.8395	$66.84	$66.85	$66.80
Purchase #2	$108.50	8.721%	$117.9623	$117.96	$117.95	$118.00
Purchase #3	$127.47	11.804%	$142.5166	$142.52	$142.50	$142.50
Purchase #4	$86.65	4.167%	$90.2607	$90.26	$90.25	$90.30
Purchase #5	$201.67	6.825%	$215.434	$215.43	$215.45	$215.40
Purchase #6	$92.25	5.697%	$97.5055	$97.51	$97.50	$97.50
Purchase #7	$223.40	6.659%	$238.2762	$238.28	$238.30	$238.30
7 purchase totals =	$899.89		$968.7948	$968.80	$968.80	$968.80