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	$68.75	5.422%	$72.4776	$72.48	$72.50	$72.50
Purchase #2	$49.95	3.600%	$51.7482	$51.75	$51.75	$51.70
Purchase #3	$131.56	3.373%	$135.9975	$136.00	$136.00	$136.00
Purchase #4	$80.45	3.626%	$83.3671	$83.37	$83.35	$83.40
Purchase #5	$100.70	10.336%	$111.1084	$111.11	$111.10	$111.10
Purchase #6	$24.90	6.514%	$26.522	$26.52	$26.50	$26.50
Purchase #7	$205.70	8.367%	$222.9109	$222.91	$222.90	$222.90
7 purchase totals =	$662.01		$704.1317	$704.14	$704.10	$704.10