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	$182.94	4.288%	$190.7845	$190.78	$190.80	$190.80
Purchase #2	$238.83	6.849%	$255.1875	$255.19	$255.20	$255.20
Purchase #3	$20.84	12.564%	$23.4583	$23.46	$23.45	$23.50
Purchase #4	$71.64	10.484%	$79.1507	$79.15	$79.15	$79.20
Purchase #5	$228.80	13.605%	$259.9282	$259.93	$259.95	$259.90
Purchase #6	$171.45	4.809%	$179.695	$179.70	$179.70	$179.70
Purchase #7	$200.68	3.842%	$208.3901	$208.39	$208.40	$208.40
7 purchase totals =	$1,115.18		$1,196.5943	$1,196.60	$1,196.65	$1,196.70