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	$31.72	3.497%	$32.8292	$32.83	$32.85	$32.80
Purchase #2	$244.64	4.803%	$256.3901	$256.39	$256.40	$256.40
Purchase #3	$20.55	5.141%	$21.6065	$21.61	$21.60	$21.60
Purchase #4	$228.79	9.386%	$250.2642	$250.26	$250.25	$250.30
Purchase #5	$105.92	3.108%	$109.212	$109.21	$109.20	$109.20
Purchase #6	$187.68	6.630%	$200.1232	$200.12	$200.10	$200.10
Purchase #7	$26.32	10.481%	$29.0786	$29.08	$29.10	$29.10
7 purchase totals =	$845.62		$899.5038	$899.50	$899.50	$899.50