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	$165.79	4.398%	$173.0814	$173.08	$173.10	$173.10
Purchase #2	$115.49	7.265%	$123.8803	$123.88	$123.90	$123.90
Purchase #3	$61.51	11.209%	$68.4047	$68.40	$68.40	$68.40
Purchase #4	$70.40	11.556%	$78.5354	$78.54	$78.55	$78.50
Purchase #5	$19.53	6.870%	$20.8717	$20.87	$20.85	$20.90
Purchase #6	$145.41	10.792%	$161.1026	$161.10	$161.10	$161.10
Purchase #7	$112.81	5.564%	$119.0867	$119.09	$119.10	$119.10
7 purchase totals =	$690.94		$744.9628	$744.96	$745.00	$745.00