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	$209.71	13.525%	$238.0733	$238.07	$238.05	$238.10
Purchase #2	$112.56	7.614%	$121.1303	$121.13	$121.15	$121.10
Purchase #3	$196.90	12.196%	$220.9139	$220.91	$220.90	$220.90
Purchase #4	$153.96	5.151%	$161.8905	$161.89	$161.90	$161.90
Purchase #5	$90.67	10.831%	$100.4905	$100.49	$100.50	$100.50
Purchase #6	$8.65	13.367%	$9.8062	$9.81	$9.80	$9.80
Purchase #7	$213.25	7.674%	$229.6148	$229.61	$229.60	$229.60
7 purchase totals =	$985.70		$1,081.9195	$1,081.91	$1,081.90	$1,081.90