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	$161.96	10.460%	$178.901	$178.90	$178.90	$178.90
Purchase #2	$92.58	6.142%	$98.2663	$98.27	$98.25	$98.30
Purchase #3	$127.60	11.354%	$142.0877	$142.09	$142.10	$142.10
Purchase #4	$126.78	12.356%	$142.4449	$142.44	$142.45	$142.40
Purchase #5	$170.76	12.694%	$192.4363	$192.44	$192.45	$192.40
Purchase #6	$71.26	13.595%	$80.9478	$80.95	$80.95	$80.90
Purchase #7	$235.53	6.540%	$250.9337	$250.93	$250.95	$250.90
7 purchase totals =	$986.47		$1,086.0177	$1,086.02	$1,086.05	$1,085.90