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	$81.81	5.547%	$86.348	$86.35	$86.35	$86.30
Purchase #2	$70.72	11.221%	$78.6555	$78.66	$78.65	$78.70
Purchase #3	$54.95	11.624%	$61.3374	$61.34	$61.35	$61.30
Purchase #4	$138.97	3.584%	$143.9507	$143.95	$143.95	$144.00
Purchase #5	$230.99	9.671%	$253.329	$253.33	$253.35	$253.30
Purchase #6	$27.53	8.546%	$29.8827	$29.88	$29.90	$29.90
Purchase #7	$25.42	13.638%	$28.8868	$28.89	$28.90	$28.90
7 purchase totals =	$630.39		$682.3901	$682.40	$682.45	$682.40