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	$180.68	8.716%	$196.4281	$196.43	$196.45	$196.40
Purchase #2	$152.70	8.594%	$165.823	$165.82	$165.80	$165.80
Purchase #3	$14.73	8.257%	$15.9463	$15.95	$15.95	$15.90
Purchase #4	$133.45	12.701%	$150.3995	$150.40	$150.40	$150.40
Purchase #5	$71.77	7.406%	$77.0853	$77.09	$77.10	$77.10
Purchase #6	$89.50	7.239%	$95.9789	$95.98	$96.00	$96.00
Purchase #7	$125.60	4.759%	$131.5773	$131.58	$131.60	$131.60
7 purchase totals =	$768.43		$833.2384	$833.25	$833.30	$833.20