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	$88.91	7.800%	$95.845	$95.85	$95.85	$95.80
Purchase #2	$105.40	8.647%	$114.5139	$114.51	$114.50	$114.50
Purchase #3	$233.37	7.752%	$251.4608	$251.46	$251.45	$251.50
Purchase #4	$198.69	12.199%	$222.9282	$222.93	$222.95	$222.90
Purchase #5	$12.95	12.235%	$14.5344	$14.53	$14.55	$14.50
Purchase #6	$237.95	13.416%	$269.8734	$269.87	$269.85	$269.90
Purchase #7	$122.93	4.450%	$128.4004	$128.40	$128.40	$128.40
7 purchase totals =	$1,000.20		$1,097.5561	$1,097.55	$1,097.55	$1,097.50