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	$202.39	6.136%	$214.8087	$214.81	$214.80	$214.80
Purchase #2	$69.43	4.850%	$72.7974	$72.80	$72.80	$72.80
Purchase #3	$115.74	5.743%	$122.3869	$122.39	$122.40	$122.40
Purchase #4	$17.40	12.320%	$19.5437	$19.54	$19.55	$19.50
Purchase #5	$71.29	10.173%	$78.5423	$78.54	$78.55	$78.50
Purchase #6	$248.54	3.149%	$256.3665	$256.37	$256.35	$256.40
Purchase #7	$48.33	5.649%	$51.0602	$51.06	$51.05	$51.10
7 purchase totals =	$773.12		$815.5057	$815.51	$815.50	$815.50