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	$14.25	8.369%	$15.4426	$15.44	$15.45	$15.40
Purchase #2	$12.31	13.286%	$13.9455	$13.95	$13.95	$13.90
Purchase #3	$71.59	10.233%	$78.9158	$78.92	$78.90	$78.90
Purchase #4	$209.88	4.481%	$219.2847	$219.28	$219.30	$219.30
Purchase #5	$144.96	9.255%	$158.376	$158.38	$158.40	$158.40
Purchase #6	$48.51	10.652%	$53.6773	$53.68	$53.70	$53.70
Purchase #7	$181.45	10.172%	$199.9071	$199.91	$199.90	$199.90
7 purchase totals =	$682.95		$739.5490	$739.56	$739.60	$739.50