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	$54.27	9.736%	$59.5537	$59.55	$59.55	$59.60
Purchase #2	$130.62	8.138%	$141.2499	$141.25	$141.25	$141.20
Purchase #3	$93.90	8.784%	$102.1482	$102.15	$102.15	$102.10
Purchase #4	$43.72	6.447%	$46.5386	$46.54	$46.55	$46.50
Purchase #5	$150.62	9.543%	$164.9937	$164.99	$165.00	$165.00
Purchase #6	$217.56	5.861%	$230.3112	$230.31	$230.30	$230.30
Purchase #7	$111.70	10.756%	$123.7145	$123.71	$123.70	$123.70
7 purchase totals =	$802.39		$868.5098	$868.50	$868.50	$868.40