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	$125.89	8.315%	$136.3578	$136.36	$136.35	$136.40
Purchase #2	$104.96	3.309%	$108.4331	$108.43	$108.45	$108.40
Purchase #3	$144.27	6.579%	$153.7615	$153.76	$153.75	$153.80
Purchase #4	$249.47	12.661%	$281.0554	$281.06	$281.05	$281.10
Purchase #5	$102.38	9.336%	$111.9382	$111.94	$111.95	$111.90
Purchase #6	$71.88	8.244%	$77.8058	$77.81	$77.80	$77.80
Purchase #7	$169.39	5.575%	$178.8335	$178.83	$178.85	$178.80
7 purchase totals =	$968.24		$1,048.1853	$1,048.19	$1,048.20	$1,048.20