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	$205.67	7.209%	$220.4968	$220.50	$220.50	$220.50
Purchase #2	$160.89	12.587%	$181.1412	$181.14	$181.15	$181.10
Purchase #3	$39.97	3.522%	$41.3777	$41.38	$41.40	$41.40
Purchase #4	$100.40	3.528%	$103.9421	$103.94	$103.95	$103.90
Purchase #5	$138.29	4.572%	$144.6126	$144.61	$144.60	$144.60
Purchase #6	$250.78	4.791%	$262.7949	$262.79	$262.80	$262.80
Purchase #7	$94.79	5.173%	$99.6935	$99.69	$99.70	$99.70
7 purchase totals =	$990.79		$1,054.0588	$1,054.05	$1,054.10	$1,054.00