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	$105.48	7.742%	$113.6463	$113.65	$113.65	$113.60
Purchase #2	$220.49	9.504%	$241.4454	$241.45	$241.45	$241.40
Purchase #3	$11.43	4.388%	$11.9315	$11.93	$11.95	$11.90
Purchase #4	$77.33	12.397%	$86.9166	$86.92	$86.90	$86.90
Purchase #5	$93.54	7.526%	$100.5798	$100.58	$100.60	$100.60
Purchase #6	$21.31	3.756%	$22.1104	$22.11	$22.10	$22.10
Purchase #7	$64.74	4.409%	$67.5944	$67.59	$67.60	$67.60
7 purchase totals =	$594.32		$644.2244	$644.23	$644.25	$644.10