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	$100.33	13.684%	$114.0592	$114.06	$114.05	$114.10
Purchase #2	$178.99	3.635%	$185.4963	$185.50	$185.50	$185.50
Purchase #3	$59.43	11.189%	$66.0796	$66.08	$66.10	$66.10
Purchase #4	$109.69	10.111%	$120.7808	$120.78	$120.80	$120.80
Purchase #5	$179.43	5.369%	$189.0636	$189.06	$189.05	$189.10
Purchase #6	$92.60	13.102%	$104.7325	$104.73	$104.75	$104.70
Purchase #7	$213.50	5.233%	$224.6725	$224.67	$224.65	$224.70
7 purchase totals =	$933.97		$1,004.8845	$1,004.88	$1,004.90	$1,005.00