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	$100.70	8.868%	$109.6301	$109.63	$109.65	$109.60
Purchase #2	$31.39	4.527%	$32.811	$32.81	$32.80	$32.80
Purchase #3	$231.52	10.700%	$256.2926	$256.29	$256.30	$256.30
Purchase #4	$210.81	11.268%	$234.5641	$234.56	$234.55	$234.60
Purchase #5	$92.36	8.622%	$100.3233	$100.32	$100.30	$100.30
Purchase #6	$171.92	5.456%	$181.3	$181.30	$181.30	$181.30
Purchase #7	$21.47	8.286%	$23.249	$23.25	$23.25	$23.20
7 purchase totals =	$860.17		$938.1701	$938.16	$938.15	$938.10