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	$131.62	11.372%	$146.5878	$146.59	$146.60	$146.60
Purchase #2	$237.86	12.692%	$268.0492	$268.05	$268.05	$268.00
Purchase #3	$220.47	12.421%	$247.8546	$247.85	$247.85	$247.90
Purchase #4	$247.86	3.132%	$255.623	$255.62	$255.60	$255.60
Purchase #5	$190.37	9.643%	$208.7274	$208.73	$208.75	$208.70
Purchase #6	$107.70	3.544%	$111.5169	$111.52	$111.50	$111.50
Purchase #7	$107.52	6.115%	$114.0948	$114.09	$114.10	$114.10
7 purchase totals =	$1,243.40		$1,352.4537	$1,352.45	$1,352.45	$1,352.40