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	$103.99	9.680%	$114.0562	$114.06	$114.05	$114.10
Purchase #2	$138.79	8.624%	$150.7592	$150.76	$150.75	$150.80
Purchase #3	$127.85	12.265%	$143.5308	$143.53	$143.55	$143.50
Purchase #4	$52.63	11.780%	$58.8298	$58.83	$58.85	$58.80
Purchase #5	$46.89	12.183%	$52.6026	$52.60	$52.60	$52.60
Purchase #6	$24.83	3.841%	$25.7837	$25.78	$25.80	$25.80
Purchase #7	$177.63	10.362%	$196.036	$196.04	$196.05	$196.00
7 purchase totals =	$672.61		$741.5983	$741.60	$741.65	$741.60