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	$119.31	3.757%	$123.7925	$123.79	$123.80	$123.80
Purchase #2	$203.87	10.736%	$225.7575	$225.76	$225.75	$225.80
Purchase #3	$148.73	6.634%	$158.5967	$158.60	$158.60	$158.60
Purchase #4	$166.39	12.335%	$186.9142	$186.91	$186.90	$186.90
Purchase #5	$145.49	13.265%	$164.7892	$164.79	$164.80	$164.80
Purchase #6	$9.53	13.156%	$10.7838	$10.78	$10.80	$10.80
Purchase #7	$200.78	7.670%	$216.1798	$216.18	$216.20	$216.20
7 purchase totals =	$994.10		$1,086.8137	$1,086.81	$1,086.85	$1,086.90