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	$59.79	8.464%	$64.8506	$64.85	$64.85	$64.90
Purchase #2	$181.29	5.325%	$190.9437	$190.94	$190.95	$190.90
Purchase #3	$103.26	13.231%	$116.9223	$116.92	$116.90	$116.90
Purchase #4	$51.30	7.280%	$55.0346	$55.03	$55.05	$55.00
Purchase #5	$249.49	8.538%	$270.7915	$270.79	$270.80	$270.80
Purchase #6	$205.80	4.521%	$215.1042	$215.10	$215.10	$215.10
Purchase #7	$130.50	13.421%	$148.0144	$148.01	$148.00	$148.00
7 purchase totals =	$981.43		$1,061.6613	$1,061.64	$1,061.65	$1,061.60