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	$99.87	3.102%	$102.968	$102.97	$102.95	$103.00
Purchase #2	$126.54	10.585%	$139.9343	$139.93	$139.95	$139.90
Purchase #3	$111.52	10.755%	$123.514	$123.51	$123.50	$123.50
Purchase #4	$10.56	6.860%	$11.2844	$11.28	$11.30	$11.30
Purchase #5	$227.39	12.381%	$255.5432	$255.54	$255.55	$255.50
Purchase #6	$183.68	13.372%	$208.2417	$208.24	$208.25	$208.20
Purchase #7	$120.27	5.243%	$126.5758	$126.58	$126.60	$126.60
7 purchase totals =	$879.83		$968.0614	$968.05	$968.10	$968.00