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	$146.86	12.522%	$165.2498	$165.25	$165.25	$165.20
Purchase #2	$248.42	5.438%	$261.9291	$261.93	$261.95	$261.90
Purchase #3	$181.62	4.792%	$190.3232	$190.32	$190.30	$190.30
Purchase #4	$136.52	10.834%	$151.3106	$151.31	$151.30	$151.30
Purchase #5	$123.67	3.848%	$128.4288	$128.43	$128.45	$128.40
Purchase #6	$161.44	13.303%	$182.9164	$182.92	$182.90	$182.90
Purchase #7	$31.84	9.665%	$34.9173	$34.92	$34.90	$34.90
7 purchase totals =	$1,030.37		$1,115.0752	$1,115.08	$1,115.05	$1,114.90