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	$243.51	6.173%	$258.5419	$258.54	$258.55	$258.50
Purchase #2	$63.83	13.184%	$72.2453	$72.25	$72.25	$72.20
Purchase #3	$128.30	11.409%	$142.9377	$142.94	$142.95	$142.90
Purchase #4	$101.43	9.484%	$111.0496	$111.05	$111.05	$111.00
Purchase #5	$225.52	13.428%	$255.8028	$255.80	$255.80	$255.80
Purchase #6	$242.33	3.683%	$251.255	$251.26	$251.25	$251.30
Purchase #7	$11.66	10.433%	$12.8765	$12.88	$12.90	$12.90
7 purchase totals =	$1,016.58		$1,104.7088	$1,104.72	$1,104.75	$1,104.60