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	$197.50	13.605%	$224.3699	$224.37	$224.35	$224.40
Purchase #2	$133.37	4.143%	$138.8955	$138.90	$138.90	$138.90
Purchase #3	$56.51	5.202%	$59.4497	$59.45	$59.45	$59.40
Purchase #4	$206.63	3.636%	$214.1431	$214.14	$214.15	$214.10
Purchase #5	$228.34	12.233%	$256.2728	$256.27	$256.25	$256.30
Purchase #6	$200.70	4.158%	$209.0451	$209.05	$209.05	$209.00
Purchase #7	$179.59	9.435%	$196.5343	$196.53	$196.55	$196.50
7 purchase totals =	$1,202.64		$1,298.7104	$1,298.71	$1,298.70	$1,298.60