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	$118.44	8.168%	$128.1142	$128.11	$128.10	$128.10
Purchase #2	$16.36	13.242%	$18.5264	$18.53	$18.55	$18.50
Purchase #3	$173.93	12.177%	$195.1095	$195.11	$195.10	$195.10
Purchase #4	$70.73	11.560%	$78.9064	$78.91	$78.90	$78.90
Purchase #5	$59.35	6.675%	$63.3116	$63.31	$63.30	$63.30
Purchase #6	$189.41	13.786%	$215.5221	$215.52	$215.50	$215.50
Purchase #7	$199.82	4.389%	$208.5901	$208.59	$208.60	$208.60
7 purchase totals =	$828.04		$908.0803	$908.08	$908.05	$908.00