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	$200.96	7.700%	$216.4339	$216.43	$216.45	$216.40
Purchase #2	$38.41	10.638%	$42.4961	$42.50	$42.50	$42.50
Purchase #3	$217.29	7.268%	$233.0826	$233.08	$233.10	$233.10
Purchase #4	$225.48	9.723%	$247.4034	$247.40	$247.40	$247.40
Purchase #5	$188.91	10.123%	$208.0334	$208.03	$208.05	$208.00
Purchase #6	$28.60	11.126%	$31.782	$31.78	$31.80	$31.80
Purchase #7	$197.38	11.139%	$219.3662	$219.37	$219.35	$219.40
7 purchase totals =	$1,097.03		$1,198.5976	$1,198.59	$1,198.65	$1,198.60