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	$167.87	5.358%	$176.8645	$176.86	$176.85	$176.90
Purchase #2	$165.46	10.309%	$182.5173	$182.52	$182.50	$182.50
Purchase #3	$160.96	3.704%	$166.922	$166.92	$166.90	$166.90
Purchase #4	$153.45	4.610%	$160.524	$160.52	$160.50	$160.50
Purchase #5	$30.45	13.575%	$34.5836	$34.58	$34.60	$34.60
Purchase #6	$28.79	9.826%	$31.6189	$31.62	$31.60	$31.60
Purchase #7	$103.29	3.128%	$106.5209	$106.52	$106.50	$106.50
7 purchase totals =	$810.27		$859.5512	$859.54	$859.45	$859.50