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	$183.94	6.232%	$195.4031	$195.40	$195.40	$195.40
Purchase #2	$196.40	9.238%	$214.5434	$214.54	$214.55	$214.50
Purchase #3	$96.37	7.371%	$103.4734	$103.47	$103.45	$103.50
Purchase #4	$209.63	6.162%	$222.5474	$222.55	$222.55	$222.50
Purchase #5	$131.67	4.461%	$137.5438	$137.54	$137.55	$137.50
Purchase #6	$111.29	13.311%	$126.1038	$126.10	$126.10	$126.10
Purchase #7	$17.74	12.434%	$19.9458	$19.95	$19.95	$19.90
7 purchase totals =	$947.04		$1,019.5607	$1,019.55	$1,019.55	$1,019.40