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	$139.55	3.827%	$144.8906	$144.89	$144.90	$144.90
Purchase #2	$237.87	11.712%	$265.7293	$265.73	$265.75	$265.70
Purchase #3	$33.88	5.548%	$35.7597	$35.76	$35.75	$35.80
Purchase #4	$56.29	6.195%	$59.7772	$59.78	$59.80	$59.80
Purchase #5	$183.53	13.526%	$208.3543	$208.35	$208.35	$208.40
Purchase #6	$157.95	4.158%	$164.5176	$164.52	$164.50	$164.50
Purchase #7	$150.35	13.454%	$170.5781	$170.58	$170.60	$170.60
7 purchase totals =	$959.42		$1,049.6068	$1,049.61	$1,049.65	$1,049.70