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	$239.35	9.686%	$262.5334	$262.53	$262.55	$262.50
Purchase #2	$115.98	12.255%	$130.1933	$130.19	$130.20	$130.20
Purchase #3	$117.98	4.372%	$123.1381	$123.14	$123.15	$123.10
Purchase #4	$75.35	4.108%	$78.4454	$78.45	$78.45	$78.40
Purchase #5	$219.51	13.389%	$248.9002	$248.90	$248.90	$248.90
Purchase #6	$144.60	4.763%	$151.4873	$151.49	$151.50	$151.50
Purchase #7	$66.31	6.811%	$70.8264	$70.83	$70.85	$70.80
7 purchase totals =	$979.08		$1,065.5241	$1,065.53	$1,065.60	$1,065.40