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	$52.62	13.752%	$59.8563	$59.86	$59.85	$59.90
Purchase #2	$63.42	5.265%	$66.7591	$66.76	$66.75	$66.80
Purchase #3	$194.43	4.852%	$203.8637	$203.86	$203.85	$203.90
Purchase #4	$59.46	8.402%	$64.4558	$64.46	$64.45	$64.50
Purchase #5	$161.75	9.118%	$176.4984	$176.50	$176.50	$176.50
Purchase #6	$207.61	11.475%	$231.4332	$231.43	$231.45	$231.40
Purchase #7	$236.54	12.498%	$266.1028	$266.10	$266.10	$266.10
7 purchase totals =	$975.83		$1,068.9693	$1,068.97	$1,068.95	$1,069.10