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	$215.78	13.611%	$245.1498	$245.15	$245.15	$245.10
Purchase #2	$103.64	10.498%	$114.5201	$114.52	$114.50	$114.50
Purchase #3	$124.72	3.359%	$128.9093	$128.91	$128.90	$128.90
Purchase #4	$167.39	7.572%	$180.0648	$180.06	$180.05	$180.10
Purchase #5	$43.93	3.593%	$45.5084	$45.51	$45.50	$45.50
Purchase #6	$220.27	4.340%	$229.8297	$229.83	$229.85	$229.80
Purchase #7	$75.94	11.545%	$84.7073	$84.71	$84.70	$84.70
7 purchase totals =	$951.67		$1,028.6894	$1,028.69	$1,028.65	$1,028.60