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	$162.59	5.159%	$170.978	$170.98	$171.00	$171.00
Purchase #2	$162.89	8.405%	$176.5809	$176.58	$176.60	$176.60
Purchase #3	$165.94	11.469%	$184.9717	$184.97	$184.95	$185.00
Purchase #4	$71.39	3.414%	$73.8273	$73.83	$73.85	$73.80
Purchase #5	$230.25	4.528%	$240.6757	$240.68	$240.70	$240.70
Purchase #6	$127.66	9.243%	$139.4596	$139.46	$139.45	$139.50
Purchase #7	$48.89	9.185%	$53.3805	$53.38	$53.40	$53.40
7 purchase totals =	$969.61		$1,039.8737	$1,039.88	$1,039.95	$1,040.00