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	$235.45	7.283%	$252.5978	$252.60	$252.60	$252.60
Purchase #2	$214.73	3.799%	$222.8876	$222.89	$222.90	$222.90
Purchase #3	$123.79	6.217%	$131.486	$131.49	$131.50	$131.50
Purchase #4	$100.73	7.216%	$107.9987	$108.00	$108.00	$108.00
Purchase #5	$106.49	6.189%	$113.0807	$113.08	$113.10	$113.10
Purchase #6	$84.50	4.791%	$88.5484	$88.55	$88.55	$88.50
Purchase #7	$139.86	13.371%	$158.5607	$158.56	$158.55	$158.60
7 purchase totals =	$1,005.55		$1,075.1599	$1,075.17	$1,075.20	$1,075.20