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	$190.37	9.739%	$208.9101	$208.91	$208.90	$208.90
Purchase #2	$217.57	5.481%	$229.495	$229.50	$229.50	$229.50
Purchase #3	$12.74	9.321%	$13.9275	$13.93	$13.95	$13.90
Purchase #4	$227.60	11.151%	$252.9797	$252.98	$253.00	$253.00
Purchase #5	$21.82	10.428%	$24.0954	$24.10	$24.10	$24.10
Purchase #6	$56.39	5.711%	$59.6104	$59.61	$59.60	$59.60
Purchase #7	$239.35	7.569%	$257.4664	$257.47	$257.45	$257.50
7 purchase totals =	$965.84		$1,046.4845	$1,046.50	$1,046.50	$1,046.50