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	$68.97	12.375%	$77.505	$77.51	$77.50	$77.50
Purchase #2	$80.36	7.643%	$86.5019	$86.50	$86.50	$86.50
Purchase #3	$66.52	12.550%	$74.8683	$74.87	$74.85	$74.90
Purchase #4	$42.31	10.824%	$46.8896	$46.89	$46.90	$46.90
Purchase #5	$216.47	7.846%	$233.4542	$233.45	$233.45	$233.50
Purchase #6	$42.95	12.386%	$48.2698	$48.27	$48.25	$48.30
Purchase #7	$197.56	9.190%	$215.7158	$215.72	$215.70	$215.70
7 purchase totals =	$715.14		$783.2046	$783.21	$783.15	$783.30