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	$107.45	8.410%	$116.4865	$116.49	$116.50	$116.50
Purchase #2	$119.52	6.794%	$127.6402	$127.64	$127.65	$127.60
Purchase #3	$75.46	8.548%	$81.9103	$81.91	$81.90	$81.90
Purchase #4	$77.33	7.200%	$82.8978	$82.90	$82.90	$82.90
Purchase #5	$151.70	4.382%	$158.3475	$158.35	$158.35	$158.30
Purchase #6	$247.85	4.850%	$259.8707	$259.87	$259.85	$259.90
Purchase #7	$67.47	4.752%	$70.6762	$70.68	$70.70	$70.70
7 purchase totals =	$846.78		$897.8292	$897.84	$897.85	$897.80