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	$247.71	5.290%	$260.8139	$260.81	$260.80	$260.80
Purchase #2	$29.80	7.625%	$32.0723	$32.07	$32.05	$32.10
Purchase #3	$72.90	13.324%	$82.6132	$82.61	$82.60	$82.60
Purchase #4	$248.76	4.129%	$259.0313	$259.03	$259.05	$259.00
Purchase #5	$108.88	13.702%	$123.7987	$123.80	$123.80	$123.80
Purchase #6	$117.87	3.827%	$122.3809	$122.38	$122.40	$122.40
Purchase #7	$183.30	12.337%	$205.9137	$205.91	$205.90	$205.90
7 purchase totals =	$1,009.22		$1,086.6240	$1,086.61	$1,086.60	$1,086.60