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	$180.87	9.499%	$198.0508	$198.05	$198.05	$198.10
Purchase #2	$128.58	10.333%	$141.8662	$141.87	$141.85	$141.90
Purchase #3	$46.91	10.563%	$51.8651	$51.87	$51.85	$51.90
Purchase #4	$131.36	10.827%	$145.5823	$145.58	$145.60	$145.60
Purchase #5	$114.92	12.157%	$128.8908	$128.89	$128.90	$128.90
Purchase #6	$89.40	6.821%	$95.498	$95.50	$95.50	$95.50
Purchase #7	$141.37	9.370%	$154.6164	$154.62	$154.60	$154.60
7 purchase totals =	$833.41		$916.3696	$916.38	$916.35	$916.50