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	$64.33	8.406%	$69.7376	$69.74	$69.75	$69.70
Purchase #2	$94.52	6.169%	$100.3509	$100.35	$100.35	$100.40
Purchase #3	$221.94	12.589%	$249.88	$249.88	$249.90	$249.90
Purchase #4	$65.83	10.258%	$72.5828	$72.58	$72.60	$72.60
Purchase #5	$95.72	9.223%	$104.5483	$104.55	$104.55	$104.50
Purchase #6	$93.25	5.707%	$98.5718	$98.57	$98.55	$98.60
Purchase #7	$234.99	13.318%	$266.286	$266.29	$266.30	$266.30
7 purchase totals =	$870.58		$961.9574	$961.96	$962.00	$962.00