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	$92.96	8.258%	$100.6366	$100.64	$100.65	$100.60
Purchase #2	$100.98	8.390%	$109.4522	$109.45	$109.45	$109.50
Purchase #3	$117.40	4.181%	$122.3085	$122.31	$122.30	$122.30
Purchase #4	$115.68	6.722%	$123.456	$123.46	$123.45	$123.50
Purchase #5	$125.95	12.794%	$142.064	$142.06	$142.05	$142.10
Purchase #6	$194.63	10.534%	$215.1323	$215.13	$215.15	$215.10
Purchase #7	$195.31	13.195%	$221.0812	$221.08	$221.10	$221.10
7 purchase totals =	$942.91		$1,034.1308	$1,034.13	$1,034.15	$1,034.20