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	$244.64	4.546%	$255.7613	$255.76	$255.75	$255.80
Purchase #2	$116.56	12.823%	$131.5065	$131.51	$131.50	$131.50
Purchase #3	$44.80	9.228%	$48.9341	$48.93	$48.95	$48.90
Purchase #4	$107.52	4.430%	$112.2831	$112.28	$112.30	$112.30
Purchase #5	$152.73	3.802%	$158.5368	$158.54	$158.55	$158.50
Purchase #6	$176.65	13.252%	$200.0597	$200.06	$200.05	$200.10
Purchase #7	$84.33	7.168%	$90.3748	$90.37	$90.35	$90.40
7 purchase totals =	$927.23		$997.4563	$997.45	$997.45	$997.50