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	$127.37	13.709%	$144.8312	$144.83	$144.85	$144.80
Purchase #2	$38.46	7.742%	$41.4376	$41.44	$41.45	$41.40
Purchase #3	$239.90	3.422%	$248.1094	$248.11	$248.10	$248.10
Purchase #4	$84.67	5.205%	$89.0771	$89.08	$89.10	$89.10
Purchase #5	$136.39	5.567%	$143.9828	$143.98	$144.00	$144.00
Purchase #6	$234.33	11.852%	$262.1028	$262.10	$262.10	$262.10
Purchase #7	$137.44	3.615%	$142.4085	$142.41	$142.40	$142.40
7 purchase totals =	$998.56		$1,071.9494	$1,071.95	$1,072.00	$1,071.90