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	$32.90	3.252%	$33.9699	$33.97	$33.95	$34.00
Purchase #2	$140.58	5.468%	$148.2669	$148.27	$148.25	$148.30
Purchase #3	$172.59	5.125%	$181.4352	$181.44	$181.45	$181.40
Purchase #4	$85.77	5.625%	$90.5946	$90.59	$90.60	$90.60
Purchase #5	$9.79	6.444%	$10.4209	$10.42	$10.40	$10.40
Purchase #6	$16.54	11.568%	$18.4533	$18.45	$18.45	$18.50
Purchase #7	$164.28	8.617%	$178.436	$178.44	$178.45	$178.40
7 purchase totals =	$622.45		$661.5768	$661.58	$661.55	$661.60