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	$242.70	10.157%	$267.351	$267.35	$267.35	$267.40
Purchase #2	$75.31	4.518%	$78.7125	$78.71	$78.70	$78.70
Purchase #3	$105.40	5.566%	$111.2666	$111.27	$111.25	$111.30
Purchase #4	$241.48	3.224%	$249.2653	$249.27	$249.25	$249.30
Purchase #5	$241.32	11.847%	$269.9092	$269.91	$269.90	$269.90
Purchase #6	$114.57	4.346%	$119.5492	$119.55	$119.55	$119.50
Purchase #7	$150.58	12.536%	$169.4567	$169.46	$169.45	$169.50
7 purchase totals =	$1,171.36		$1,265.5105	$1,265.52	$1,265.45	$1,265.60