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	$107.71	3.117%	$111.0673	$111.07	$111.05	$111.10
Purchase #2	$143.89	7.803%	$155.1177	$155.12	$155.10	$155.10
Purchase #3	$237.31	10.677%	$262.6476	$262.65	$262.65	$262.60
Purchase #4	$191.56	4.622%	$200.4139	$200.41	$200.40	$200.40
Purchase #5	$25.28	12.599%	$28.465	$28.47	$28.45	$28.50
Purchase #6	$108.37	5.227%	$114.0345	$114.03	$114.05	$114.00
Purchase #7	$231.87	7.120%	$248.3791	$248.38	$248.40	$248.40
7 purchase totals =	$1,045.99		$1,120.1251	$1,120.13	$1,120.10	$1,120.10