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	$68.86	5.826%	$72.8718	$72.87	$72.85	$72.90
Purchase #2	$15.70	9.550%	$17.1994	$17.20	$17.20	$17.20
Purchase #3	$94.86	6.255%	$100.7935	$100.79	$100.80	$100.80
Purchase #4	$169.56	12.797%	$191.2586	$191.26	$191.25	$191.30
Purchase #5	$153.58	9.692%	$168.465	$168.47	$168.45	$168.50
Purchase #6	$231.51	9.681%	$253.9225	$253.92	$253.90	$253.90
Purchase #7	$76.83	5.853%	$81.3269	$81.33	$81.35	$81.30
7 purchase totals =	$810.90		$885.8377	$885.84	$885.80	$885.90