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	$205.33	9.644%	$225.132	$225.13	$225.15	$225.10
Purchase #2	$75.38	10.683%	$83.4328	$83.43	$83.45	$83.40
Purchase #3	$14.55	9.482%	$15.9296	$15.93	$15.95	$15.90
Purchase #4	$151.72	4.527%	$158.5884	$158.59	$158.60	$158.60
Purchase #5	$54.68	11.152%	$60.7779	$60.78	$60.80	$60.80
Purchase #6	$144.42	7.544%	$155.315	$155.32	$155.30	$155.30
Purchase #7	$250.47	11.147%	$278.3899	$278.39	$278.40	$278.40
7 purchase totals =	$896.55		$977.5656	$977.57	$977.65	$977.50