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	$45.54	6.581%	$48.537	$48.54	$48.55	$48.50
Purchase #2	$214.84	3.243%	$221.8073	$221.81	$221.80	$221.80
Purchase #3	$173.38	8.350%	$187.8572	$187.86	$187.85	$187.90
Purchase #4	$121.45	5.810%	$128.5062	$128.51	$128.50	$128.50
Purchase #5	$118.75	3.872%	$123.348	$123.35	$123.35	$123.30
Purchase #6	$164.83	13.429%	$186.965	$186.97	$186.95	$187.00
Purchase #7	$130.68	5.129%	$137.3826	$137.38	$137.40	$137.40
7 purchase totals =	$969.47		$1,034.4033	$1,034.42	$1,034.40	$1,034.40