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	$11.75	8.150%	$12.7076	$12.71	$12.70	$12.70
Purchase #2	$55.98	13.436%	$63.5015	$63.50	$63.50	$63.50
Purchase #3	$246.53	6.445%	$262.4189	$262.42	$262.40	$262.40
Purchase #4	$36.87	7.126%	$39.4974	$39.50	$39.50	$39.50
Purchase #5	$81.37	11.467%	$90.7007	$90.70	$90.70	$90.70
Purchase #6	$62.69	7.615%	$67.4638	$67.46	$67.45	$67.50
Purchase #7	$249.83	6.838%	$266.9134	$266.91	$266.90	$266.90
7 purchase totals =	$745.02		$803.2033	$803.20	$803.15	$803.20