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	$49.43	7.848%	$53.3093	$53.31	$53.30	$53.30
Purchase #2	$101.98	5.495%	$107.5838	$107.58	$107.60	$107.60
Purchase #3	$114.95	7.425%	$123.485	$123.49	$123.50	$123.50
Purchase #4	$80.35	3.579%	$83.2257	$83.23	$83.25	$83.20
Purchase #5	$235.92	8.153%	$255.1546	$255.15	$255.15	$255.20
Purchase #6	$174.92	12.429%	$196.6608	$196.66	$196.65	$196.70
Purchase #7	$208.73	13.246%	$236.3784	$236.38	$236.40	$236.40
7 purchase totals =	$966.28		$1,055.7976	$1,055.80	$1,055.85	$1,055.90