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	$223.80	11.298%	$249.0849	$249.08	$249.10	$249.10
Purchase #2	$111.32	9.469%	$121.8609	$121.86	$121.85	$121.90
Purchase #3	$117.40	12.152%	$131.6664	$131.67	$131.65	$131.70
Purchase #4	$229.60	5.322%	$241.8193	$241.82	$241.80	$241.80
Purchase #5	$164.53	8.859%	$179.1057	$179.11	$179.10	$179.10
Purchase #6	$47.67	9.346%	$52.1252	$52.13	$52.15	$52.10
Purchase #7	$64.95	4.590%	$67.9312	$67.93	$67.95	$67.90
7 purchase totals =	$959.27		$1,043.5936	$1,043.60	$1,043.60	$1,043.60