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	$104.46	5.845%	$110.5657	$110.57	$110.55	$110.60
Purchase #2	$45.73	5.169%	$48.0938	$48.09	$48.10	$48.10
Purchase #3	$127.29	10.484%	$140.6351	$140.64	$140.65	$140.60
Purchase #4	$220.66	12.779%	$248.8581	$248.86	$248.85	$248.90
Purchase #5	$120.49	6.215%	$127.9785	$127.98	$128.00	$128.00
Purchase #6	$159.40	3.268%	$164.6092	$164.61	$164.60	$164.60
Purchase #7	$186.82	9.404%	$204.3886	$204.39	$204.40	$204.40
7 purchase totals =	$964.85		$1,045.1290	$1,045.14	$1,045.15	$1,045.20