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	$70.43	7.105%	$75.4341	$75.43	$75.45	$75.40
Purchase #2	$220.83	4.236%	$230.1844	$230.18	$230.20	$230.20
Purchase #3	$66.26	8.195%	$71.69	$71.69	$71.70	$71.70
Purchase #4	$21.74	3.259%	$22.4485	$22.45	$22.45	$22.40
Purchase #5	$208.51	6.812%	$222.7137	$222.71	$222.70	$222.70
Purchase #6	$73.93	6.387%	$78.6519	$78.65	$78.65	$78.70
Purchase #7	$81.87	4.178%	$85.2905	$85.29	$85.30	$85.30
7 purchase totals =	$743.57		$786.4131	$786.40	$786.45	$786.40