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	$96.33	12.339%	$108.2162	$108.22	$108.20	$108.20
Purchase #2	$183.66	6.735%	$196.0295	$196.03	$196.05	$196.00
Purchase #3	$33.48	9.593%	$36.6917	$36.69	$36.70	$36.70
Purchase #4	$239.37	3.529%	$247.8174	$247.82	$247.80	$247.80
Purchase #5	$136.45	5.661%	$144.1744	$144.17	$144.15	$144.20
Purchase #6	$97.90	11.798%	$109.4502	$109.45	$109.45	$109.50
Purchase #7	$120.52	3.560%	$124.8105	$124.81	$124.80	$124.80
7 purchase totals =	$907.71		$967.1899	$967.19	$967.15	$967.20