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	$207.55	10.548%	$229.4424	$229.44	$229.45	$229.40
Purchase #2	$237.93	13.536%	$270.1362	$270.14	$270.15	$270.10
Purchase #3	$58.81	8.342%	$63.7159	$63.72	$63.70	$63.70
Purchase #4	$13.47	3.767%	$13.9774	$13.98	$14.00	$14.00
Purchase #5	$158.83	12.809%	$179.1745	$179.17	$179.15	$179.20
Purchase #6	$159.29	12.465%	$179.1455	$179.15	$179.15	$179.10
Purchase #7	$89.27	12.121%	$100.0904	$100.09	$100.10	$100.10
7 purchase totals =	$925.15		$1,035.6823	$1,035.69	$1,035.70	$1,035.60