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	$152.82	10.190%	$168.3924	$168.39	$168.40	$168.40
Purchase #2	$138.96	7.115%	$148.847	$148.85	$148.85	$148.80
Purchase #3	$161.43	7.411%	$173.3936	$173.39	$173.40	$173.40
Purchase #4	$103.42	9.155%	$112.8881	$112.89	$112.90	$112.90
Purchase #5	$138.83	11.607%	$154.944	$154.94	$154.95	$154.90
Purchase #6	$226.69	3.204%	$233.9531	$233.95	$233.95	$234.00
Purchase #7	$129.55	11.839%	$144.8874	$144.89	$144.90	$144.90
7 purchase totals =	$1,051.70		$1,137.3056	$1,137.30	$1,137.35	$1,137.30