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	$61.54	4.686%	$64.4238	$64.42	$64.40	$64.40
Purchase #2	$69.88	3.857%	$72.5753	$72.58	$72.60	$72.60
Purchase #3	$55.78	9.426%	$61.0378	$61.04	$61.05	$61.00
Purchase #4	$109.65	8.358%	$118.8145	$118.81	$118.80	$118.80
Purchase #5	$222.44	13.576%	$252.6385	$252.64	$252.65	$252.60
Purchase #6	$140.63	6.874%	$150.2969	$150.30	$150.30	$150.30
Purchase #7	$158.81	4.226%	$165.5213	$165.52	$165.50	$165.50
7 purchase totals =	$818.73		$885.3081	$885.31	$885.30	$885.20