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	$206.60	7.829%	$222.7747	$222.77	$222.75	$222.80
Purchase #2	$111.58	10.335%	$123.1118	$123.11	$123.10	$123.10
Purchase #3	$174.64	12.679%	$196.7826	$196.78	$196.80	$196.80
Purchase #4	$98.31	10.320%	$108.4556	$108.46	$108.45	$108.50
Purchase #5	$59.28	9.808%	$65.0942	$65.09	$65.10	$65.10
Purchase #6	$185.32	13.840%	$210.9683	$210.97	$210.95	$211.00
Purchase #7	$5.39	10.202%	$5.9399	$5.94	$5.95	$5.90
7 purchase totals =	$841.12		$933.1271	$933.12	$933.10	$933.20