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	$166.62	9.743%	$182.8538	$182.85	$182.85	$182.90
Purchase #2	$184.73	11.205%	$205.429	$205.43	$205.45	$205.40
Purchase #3	$73.41	3.789%	$76.1915	$76.19	$76.20	$76.20
Purchase #4	$200.41	4.196%	$208.8192	$208.82	$208.80	$208.80
Purchase #5	$123.60	3.291%	$127.6677	$127.67	$127.65	$127.70
Purchase #6	$155.46	10.324%	$171.5097	$171.51	$171.50	$171.50
Purchase #7	$107.87	13.864%	$122.8251	$122.83	$122.85	$122.80
7 purchase totals =	$1,012.10		$1,095.2960	$1,095.30	$1,095.30	$1,095.30