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	$218.36	13.859%	$248.6225	$248.62	$248.60	$248.60
Purchase #2	$120.77	13.747%	$137.3723	$137.37	$137.35	$137.40
Purchase #3	$164.61	8.436%	$178.4965	$178.50	$178.50	$178.50
Purchase #4	$202.79	13.446%	$230.0571	$230.06	$230.05	$230.10
Purchase #5	$128.94	12.246%	$144.73	$144.73	$144.75	$144.70
Purchase #6	$108.28	3.354%	$111.9117	$111.91	$111.90	$111.90
Purchase #7	$26.86	10.197%	$29.5989	$29.60	$29.60	$29.60
7 purchase totals =	$970.61		$1,080.7890	$1,080.79	$1,080.75	$1,080.80