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	$95.74	3.219%	$98.8219	$98.82	$98.80	$98.80
Purchase #2	$158.48	11.423%	$176.5832	$176.58	$176.60	$176.60
Purchase #3	$10.48	5.321%	$11.0376	$11.04	$11.05	$11.00
Purchase #4	$138.75	10.228%	$152.9414	$152.94	$152.95	$152.90
Purchase #5	$132.40	4.728%	$138.6599	$138.66	$138.65	$138.70
Purchase #6	$89.95	11.430%	$100.2313	$100.23	$100.25	$100.20
Purchase #7	$140.81	12.410%	$158.2845	$158.28	$158.30	$158.30
7 purchase totals =	$766.61		$836.5598	$836.55	$836.60	$836.50