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	$148.54	11.453%	$165.5523	$165.55	$165.55	$165.60
Purchase #2	$245.52	4.628%	$256.8827	$256.88	$256.90	$256.90
Purchase #3	$239.79	9.788%	$263.2606	$263.26	$263.25	$263.30
Purchase #4	$95.91	4.291%	$100.0255	$100.03	$100.05	$100.00
Purchase #5	$164.99	13.142%	$186.673	$186.67	$186.65	$186.70
Purchase #6	$59.71	4.810%	$62.5821	$62.58	$62.60	$62.60
Purchase #7	$38.38	6.333%	$40.8106	$40.81	$40.80	$40.80
7 purchase totals =	$992.84		$1,075.7868	$1,075.78	$1,075.80	$1,075.90