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	$163.80	7.142%	$175.4986	$175.50	$175.50	$175.50
Purchase #2	$42.96	7.365%	$46.124	$46.12	$46.10	$46.10
Purchase #3	$245.47	11.137%	$272.808	$272.81	$272.80	$272.80
Purchase #4	$6.60	13.176%	$7.4696	$7.47	$7.45	$7.50
Purchase #5	$11.47	12.308%	$12.8817	$12.88	$12.90	$12.90
Purchase #6	$133.31	8.139%	$144.1601	$144.16	$144.15	$144.20
Purchase #7	$201.78	4.846%	$211.5583	$211.56	$211.55	$211.60
7 purchase totals =	$805.39		$870.5003	$870.50	$870.45	$870.60