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	$144.83	7.227%	$155.2969	$155.30	$155.30	$155.30
Purchase #2	$97.57	4.211%	$101.6787	$101.68	$101.70	$101.70
Purchase #3	$81.83	5.742%	$86.5287	$86.53	$86.55	$86.50
Purchase #4	$197.99	12.334%	$222.4101	$222.41	$222.40	$222.40
Purchase #5	$246.67	3.403%	$255.0642	$255.06	$255.05	$255.10
Purchase #6	$172.43	8.470%	$187.0348	$187.03	$187.05	$187.00
Purchase #7	$39.82	4.232%	$41.5052	$41.51	$41.50	$41.50
7 purchase totals =	$981.14		$1,049.5186	$1,049.52	$1,049.55	$1,049.50