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	$42.94	4.359%	$44.8118	$44.81	$44.80	$44.80
Purchase #2	$92.27	11.832%	$103.1874	$103.19	$103.20	$103.20
Purchase #3	$55.87	4.602%	$58.4411	$58.44	$58.45	$58.40
Purchase #4	$59.65	11.161%	$66.3075	$66.31	$66.30	$66.30
Purchase #5	$111.64	6.652%	$119.0663	$119.07	$119.05	$119.10
Purchase #6	$71.71	12.216%	$80.4701	$80.47	$80.45	$80.50
Purchase #7	$11.51	13.839%	$13.1029	$13.10	$13.10	$13.10
7 purchase totals =	$445.59		$485.3871	$485.39	$485.35	$485.40