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	$242.53	8.313%	$262.6915	$262.69	$262.70	$262.70
Purchase #2	$159.86	6.326%	$169.9727	$169.97	$169.95	$170.00
Purchase #3	$50.55	12.470%	$56.8536	$56.85	$56.85	$56.90
Purchase #4	$75.82	7.705%	$81.6619	$81.66	$81.65	$81.70
Purchase #5	$100.46	10.733%	$111.2424	$111.24	$111.25	$111.20
Purchase #6	$179.91	3.118%	$185.5196	$185.52	$185.50	$185.50
Purchase #7	$207.49	3.121%	$213.9658	$213.97	$213.95	$214.00
7 purchase totals =	$1,016.62		$1,081.9075	$1,081.90	$1,081.85	$1,082.00