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	$66.81	5.453%	$70.4531	$70.45	$70.45	$70.50
Purchase #2	$160.47	13.144%	$181.5622	$181.56	$181.55	$181.60
Purchase #3	$218.43	4.603%	$228.4843	$228.48	$228.50	$228.50
Purchase #4	$36.61	5.452%	$38.606	$38.61	$38.60	$38.60
Purchase #5	$162.90	6.492%	$173.4755	$173.48	$173.50	$173.50
Purchase #6	$42.67	12.504%	$48.0055	$48.01	$48.00	$48.00
Purchase #7	$166.58	7.192%	$178.5604	$178.56	$178.55	$178.60
7 purchase totals =	$854.47		$919.1470	$919.15	$919.15	$919.30