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	$61.83	9.623%	$67.7799	$67.78	$67.80	$67.80
Purchase #2	$51.95	11.669%	$58.012	$58.01	$58.00	$58.00
Purchase #3	$22.42	13.788%	$25.5113	$25.51	$25.50	$25.50
Purchase #4	$163.25	7.744%	$175.8921	$175.89	$175.90	$175.90
Purchase #5	$67.59	7.818%	$72.8742	$72.87	$72.85	$72.90
Purchase #6	$118.26	11.837%	$132.2584	$132.26	$132.25	$132.30
Purchase #7	$46.88	8.301%	$50.7715	$50.77	$50.75	$50.80
7 purchase totals =	$532.18		$583.0994	$583.09	$583.05	$583.20