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	$208.77	6.245%	$221.8077	$221.81	$221.80	$221.80
Purchase #2	$216.90	9.685%	$237.9068	$237.91	$237.90	$237.90
Purchase #3	$78.28	9.152%	$85.4442	$85.44	$85.45	$85.40
Purchase #4	$98.38	10.690%	$108.8968	$108.90	$108.90	$108.90
Purchase #5	$38.39	3.190%	$39.6146	$39.61	$39.60	$39.60
Purchase #6	$181.78	4.844%	$190.5854	$190.59	$190.60	$190.60
Purchase #7	$176.48	10.223%	$194.5216	$194.52	$194.50	$194.50
7 purchase totals =	$998.98		$1,078.7771	$1,078.78	$1,078.75	$1,078.70