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	$180.39	13.860%	$205.3921	$205.39	$205.40	$205.40
Purchase #2	$50.82	7.723%	$54.7448	$54.74	$54.75	$54.70
Purchase #3	$45.43	7.539%	$48.855	$48.86	$48.85	$48.90
Purchase #4	$85.99	3.846%	$89.2972	$89.30	$89.30	$89.30
Purchase #5	$131.77	4.439%	$137.6193	$137.62	$137.60	$137.60
Purchase #6	$83.52	9.147%	$91.1596	$91.16	$91.15	$91.20
Purchase #7	$85.98	13.393%	$97.4953	$97.50	$97.50	$97.50
7 purchase totals =	$663.90		$724.5633	$724.57	$724.55	$724.60