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	$212.88	5.244%	$224.0434	$224.04	$224.05	$224.00
Purchase #2	$40.45	3.622%	$41.9151	$41.92	$41.90	$41.90
Purchase #3	$63.38	11.856%	$70.8943	$70.89	$70.90	$70.90
Purchase #4	$230.43	10.527%	$254.6874	$254.69	$254.70	$254.70
Purchase #5	$145.84	7.764%	$157.163	$157.16	$157.15	$157.20
Purchase #6	$209.74	8.447%	$227.4567	$227.46	$227.45	$227.50
Purchase #7	$98.82	12.697%	$111.3672	$111.37	$111.35	$111.40
7 purchase totals =	$1,001.54		$1,087.5271	$1,087.53	$1,087.50	$1,087.60