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	$217.80	7.345%	$233.7974	$233.80	$233.80	$233.80
Purchase #2	$21.81	10.838%	$24.1738	$24.17	$24.15	$24.20
Purchase #3	$82.51	12.258%	$92.6241	$92.62	$92.60	$92.60
Purchase #4	$27.83	3.653%	$28.8466	$28.85	$28.85	$28.80
Purchase #5	$171.82	4.672%	$179.8474	$179.85	$179.85	$179.80
Purchase #6	$33.37	6.789%	$35.6355	$35.64	$35.65	$35.60
Purchase #7	$125.38	13.478%	$142.2787	$142.28	$142.30	$142.30
7 purchase totals =	$680.52		$737.2035	$737.21	$737.20	$737.10