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	$95.86	13.293%	$108.6027	$108.60	$108.60	$108.60
Purchase #2	$38.70	4.506%	$40.4438	$40.44	$40.45	$40.40
Purchase #3	$203.46	8.207%	$220.158	$220.16	$220.15	$220.20
Purchase #4	$169.34	11.306%	$188.4856	$188.49	$188.50	$188.50
Purchase #5	$159.53	4.616%	$166.8939	$166.89	$166.90	$166.90
Purchase #6	$164.88	5.471%	$173.9006	$173.90	$173.90	$173.90
Purchase #7	$217.51	11.302%	$242.093	$242.09	$242.10	$242.10
7 purchase totals =	$1,049.28		$1,140.5776	$1,140.57	$1,140.60	$1,140.60