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	$233.39	11.300%	$259.7631	$259.76	$259.75	$259.80
Purchase #2	$207.47	12.329%	$233.049	$233.05	$233.05	$233.00
Purchase #3	$112.37	7.157%	$120.4123	$120.41	$120.40	$120.40
Purchase #4	$214.34	3.611%	$222.0798	$222.08	$222.10	$222.10
Purchase #5	$143.55	10.341%	$158.3945	$158.39	$158.40	$158.40
Purchase #6	$111.71	10.583%	$123.5323	$123.53	$123.55	$123.50
Purchase #7	$103.46	5.499%	$109.1493	$109.15	$109.15	$109.10
7 purchase totals =	$1,126.29		$1,226.3803	$1,226.37	$1,226.40	$1,226.30