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	$95.28	11.661%	$106.3906	$106.39	$106.40	$106.40
Purchase #2	$16.84	12.627%	$18.9664	$18.97	$18.95	$19.00
Purchase #3	$110.92	11.382%	$123.5449	$123.54	$123.55	$123.50
Purchase #4	$61.29	3.256%	$63.2856	$63.29	$63.30	$63.30
Purchase #5	$228.47	5.193%	$240.3344	$240.33	$240.35	$240.30
Purchase #6	$151.98	7.470%	$163.3329	$163.33	$163.35	$163.30
Purchase #7	$39.76	7.137%	$42.5977	$42.60	$42.60	$42.60
7 purchase totals =	$704.54		$758.4525	$758.45	$758.50	$758.40