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	$102.51	6.751%	$109.4305	$109.43	$109.45	$109.40
Purchase #2	$100.31	3.141%	$103.4607	$103.46	$103.45	$103.50
Purchase #3	$33.69	3.242%	$34.7822	$34.78	$34.80	$34.80
Purchase #4	$116.55	8.207%	$126.1153	$126.12	$126.10	$126.10
Purchase #5	$138.62	3.688%	$143.7323	$143.73	$143.75	$143.70
Purchase #6	$39.95	3.758%	$41.4513	$41.45	$41.45	$41.50
Purchase #7	$150.41	3.153%	$155.1524	$155.15	$155.15	$155.20
7 purchase totals =	$682.04		$714.1247	$714.12	$714.15	$714.20