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	$38.69	13.149%	$43.7773	$43.78	$43.80	$43.80
Purchase #2	$59.71	8.168%	$64.5871	$64.59	$64.60	$64.60
Purchase #3	$148.84	7.609%	$160.1652	$160.17	$160.15	$160.20
Purchase #4	$191.79	4.618%	$200.6469	$200.65	$200.65	$200.60
Purchase #5	$205.39	12.693%	$231.4602	$231.46	$231.45	$231.50
Purchase #6	$116.41	10.823%	$129.0091	$129.01	$129.00	$129.00
Purchase #7	$96.58	7.291%	$103.6216	$103.62	$103.60	$103.60
7 purchase totals =	$857.41		$933.2674	$933.28	$933.25	$933.30