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	$181.86	10.265%	$200.5279	$200.53	$200.55	$200.50
Purchase #2	$132.34	4.716%	$138.5812	$138.58	$138.60	$138.60
Purchase #3	$62.76	12.759%	$70.7675	$70.77	$70.75	$70.80
Purchase #4	$42.56	13.848%	$48.4537	$48.45	$48.45	$48.50
Purchase #5	$38.76	3.323%	$40.048	$40.05	$40.05	$40.00
Purchase #6	$169.64	13.348%	$192.2835	$192.28	$192.30	$192.30
Purchase #7	$64.37	12.559%	$72.4542	$72.45	$72.45	$72.50
7 purchase totals =	$692.29		$763.1160	$763.11	$763.15	$763.20