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	$69.58	9.802%	$76.4002	$76.40	$76.40	$76.40
Purchase #2	$129.97	5.726%	$137.4121	$137.41	$137.40	$137.40
Purchase #3	$160.93	7.718%	$173.3506	$173.35	$173.35	$173.40
Purchase #4	$83.87	3.138%	$86.5018	$86.50	$86.50	$86.50
Purchase #5	$153.56	4.698%	$160.7742	$160.77	$160.75	$160.80
Purchase #6	$138.68	10.236%	$152.8753	$152.88	$152.90	$152.90
Purchase #7	$176.30	11.697%	$196.9218	$196.92	$196.90	$196.90
7 purchase totals =	$912.89		$984.2360	$984.23	$984.20	$984.30