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	$125.80	5.257%	$132.4133	$132.41	$132.40	$132.40
Purchase #2	$42.55	11.474%	$47.4322	$47.43	$47.45	$47.40
Purchase #3	$97.94	7.483%	$105.2689	$105.27	$105.25	$105.30
Purchase #4	$190.64	11.798%	$213.1317	$213.13	$213.15	$213.10
Purchase #5	$148.46	10.508%	$164.0602	$164.06	$164.05	$164.10
Purchase #6	$88.46	11.690%	$98.801	$98.80	$98.80	$98.80
Purchase #7	$134.54	7.345%	$144.422	$144.42	$144.40	$144.40
7 purchase totals =	$828.39		$905.5293	$905.52	$905.50	$905.50