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	$222.93	7.142%	$238.8517	$238.85	$238.85	$238.90
Purchase #2	$111.84	10.369%	$123.4367	$123.44	$123.45	$123.40
Purchase #3	$115.48	9.503%	$126.4541	$126.45	$126.45	$126.50
Purchase #4	$161.39	7.697%	$173.8122	$173.81	$173.80	$173.80
Purchase #5	$233.78	7.342%	$250.9441	$250.94	$250.95	$250.90
Purchase #6	$158.32	11.709%	$176.8577	$176.86	$176.85	$176.90
Purchase #7	$148.85	10.780%	$164.896	$164.90	$164.90	$164.90
7 purchase totals =	$1,152.59		$1,255.2525	$1,255.25	$1,255.25	$1,255.30