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	$47.94	10.362%	$52.9075	$52.91	$52.90	$52.90
Purchase #2	$175.91	8.834%	$191.4499	$191.45	$191.45	$191.40
Purchase #3	$48.89	6.319%	$51.9794	$51.98	$52.00	$52.00
Purchase #4	$87.59	6.685%	$93.4454	$93.45	$93.45	$93.40
Purchase #5	$144.84	4.654%	$151.5809	$151.58	$151.60	$151.60
Purchase #6	$133.52	11.461%	$148.8227	$148.82	$148.80	$148.80
Purchase #7	$156.93	10.811%	$173.8957	$173.90	$173.90	$173.90
7 purchase totals =	$795.62		$864.0815	$864.09	$864.10	$864.00