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	$198.51	9.621%	$217.6086	$217.61	$217.60	$217.60
Purchase #2	$21.81	5.202%	$22.9446	$22.94	$22.95	$22.90
Purchase #3	$68.78	6.800%	$73.457	$73.46	$73.45	$73.50
Purchase #4	$89.67	12.432%	$100.8178	$100.82	$100.80	$100.80
Purchase #5	$92.81	7.469%	$99.742	$99.74	$99.75	$99.70
Purchase #6	$176.42	4.265%	$183.9443	$183.94	$183.95	$183.90
Purchase #7	$117.46	5.487%	$123.905	$123.91	$123.90	$123.90
7 purchase totals =	$765.46		$822.4193	$822.42	$822.40	$822.30