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	$113.86	7.266%	$122.1331	$122.13	$122.15	$122.10
Purchase #2	$242.69	4.160%	$252.7859	$252.79	$252.80	$252.80
Purchase #3	$204.49	6.565%	$217.9148	$217.91	$217.90	$217.90
Purchase #4	$125.69	11.750%	$140.4586	$140.46	$140.45	$140.50
Purchase #5	$47.69	10.640%	$52.7642	$52.76	$52.75	$52.80
Purchase #6	$56.89	5.162%	$59.8267	$59.83	$59.85	$59.80
Purchase #7	$123.32	6.580%	$131.4345	$131.43	$131.45	$131.40
7 purchase totals =	$914.63		$977.3178	$977.31	$977.35	$977.30