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	$112.62	9.462%	$123.2761	$123.28	$123.30	$123.30
Purchase #2	$234.85	10.867%	$260.3711	$260.37	$260.35	$260.40
Purchase #3	$112.58	10.337%	$124.2174	$124.22	$124.20	$124.20
Purchase #4	$205.27	11.204%	$228.2685	$228.27	$228.25	$228.30
Purchase #5	$107.60	11.419%	$119.8868	$119.89	$119.90	$119.90
Purchase #6	$152.52	13.231%	$172.6999	$172.70	$172.70	$172.70
Purchase #7	$45.25	3.577%	$46.8686	$46.87	$46.85	$46.90
7 purchase totals =	$970.69		$1,075.5884	$1,075.60	$1,075.55	$1,075.70