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	$216.32	7.135%	$231.7544	$231.75	$231.75	$231.80
Purchase #2	$98.28	5.772%	$103.9527	$103.95	$103.95	$104.00
Purchase #3	$84.78	12.325%	$95.2291	$95.23	$95.25	$95.20
Purchase #4	$26.53	11.606%	$29.6091	$29.61	$29.60	$29.60
Purchase #5	$122.79	4.190%	$127.9349	$127.93	$127.95	$127.90
Purchase #6	$141.94	6.381%	$150.9972	$151.00	$151.00	$151.00
Purchase #7	$137.75	9.156%	$150.3624	$150.36	$150.35	$150.40
7 purchase totals =	$828.39		$889.8398	$889.83	$889.85	$889.90