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	$81.50	10.752%	$90.2629	$90.26	$90.25	$90.30
Purchase #2	$11.72	10.477%	$12.9479	$12.95	$12.95	$12.90
Purchase #3	$237.65	10.705%	$263.0904	$263.09	$263.10	$263.10
Purchase #4	$164.68	6.506%	$175.3941	$175.39	$175.40	$175.40
Purchase #5	$199.63	8.673%	$216.9439	$216.94	$216.95	$216.90
Purchase #6	$154.72	11.451%	$172.437	$172.44	$172.45	$172.40
Purchase #7	$108.60	3.715%	$112.6345	$112.63	$112.65	$112.60
7 purchase totals =	$958.50		$1,043.7107	$1,043.70	$1,043.75	$1,043.60