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	$205.54	11.756%	$229.7033	$229.70	$229.70	$229.70
Purchase #2	$248.50	3.177%	$256.3948	$256.39	$256.40	$256.40
Purchase #3	$43.92	13.722%	$49.9467	$49.95	$49.95	$49.90
Purchase #4	$152.88	7.401%	$164.1946	$164.19	$164.20	$164.20
Purchase #5	$57.29	4.409%	$59.8159	$59.82	$59.80	$59.80
Purchase #6	$140.95	5.710%	$148.9982	$149.00	$149.00	$149.00
Purchase #7	$178.94	9.832%	$196.5334	$196.53	$196.55	$196.50
7 purchase totals =	$1,028.02		$1,105.5869	$1,105.58	$1,105.60	$1,105.50