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	$72.45	8.319%	$78.4771	$78.48	$78.50	$78.50
Purchase #2	$233.25	11.350%	$259.7239	$259.72	$259.70	$259.70
Purchase #3	$37.86	3.191%	$39.0681	$39.07	$39.05	$39.10
Purchase #4	$184.49	8.836%	$200.7915	$200.79	$200.80	$200.80
Purchase #5	$153.49	8.491%	$166.5228	$166.52	$166.50	$166.50
Purchase #6	$45.88	6.655%	$48.9333	$48.93	$48.95	$48.90
Purchase #7	$163.44	3.204%	$168.6766	$168.68	$168.70	$168.70
7 purchase totals =	$890.86		$962.1933	$962.19	$962.20	$962.20