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	$127.69	13.410%	$144.8132	$144.81	$144.80	$144.80
Purchase #2	$191.58	4.786%	$200.749	$200.75	$200.75	$200.70
Purchase #3	$161.40	4.395%	$168.4935	$168.49	$168.50	$168.50
Purchase #4	$216.86	11.858%	$242.5753	$242.58	$242.60	$242.60
Purchase #5	$105.81	5.642%	$111.7798	$111.78	$111.80	$111.80
Purchase #6	$88.81	13.381%	$100.6937	$100.69	$100.70	$100.70
Purchase #7	$171.28	9.384%	$187.3529	$187.35	$187.35	$187.40
7 purchase totals =	$1,063.43		$1,156.4574	$1,156.45	$1,156.50	$1,156.50