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	$157.83	5.129%	$165.9251	$165.93	$165.95	$165.90
Purchase #2	$130.80	6.546%	$139.3622	$139.36	$139.35	$139.40
Purchase #3	$49.58	5.434%	$52.2742	$52.27	$52.25	$52.30
Purchase #4	$20.89	4.609%	$21.8528	$21.85	$21.85	$21.90
Purchase #5	$72.26	5.195%	$76.0139	$76.01	$76.00	$76.00
Purchase #6	$12.42	11.350%	$13.8297	$13.83	$13.85	$13.80
Purchase #7	$165.56	11.176%	$184.063	$184.06	$184.05	$184.10
7 purchase totals =	$609.34		$653.3209	$653.31	$653.30	$653.40