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	$106.54	4.494%	$111.3279	$111.33	$111.35	$111.30
Purchase #2	$146.75	6.608%	$156.4472	$156.45	$156.45	$156.40
Purchase #3	$235.55	11.604%	$262.8832	$262.88	$262.90	$262.90
Purchase #4	$45.65	6.116%	$48.442	$48.44	$48.45	$48.40
Purchase #5	$126.91	11.860%	$141.9615	$141.96	$141.95	$142.00
Purchase #6	$21.74	7.203%	$23.3059	$23.31	$23.30	$23.30
Purchase #7	$137.93	9.418%	$150.9202	$150.92	$150.90	$150.90
7 purchase totals =	$821.07		$895.2879	$895.29	$895.30	$895.20