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	$70.27	4.751%	$73.6085	$73.61	$73.60	$73.60
Purchase #2	$78.27	9.648%	$85.8215	$85.82	$85.80	$85.80
Purchase #3	$160.34	10.265%	$176.7989	$176.80	$176.80	$176.80
Purchase #4	$100.40	3.104%	$103.5164	$103.52	$103.50	$103.50
Purchase #5	$117.96	7.630%	$126.9603	$126.96	$126.95	$127.00
Purchase #6	$49.37	9.192%	$53.9081	$53.91	$53.90	$53.90
Purchase #7	$214.67	3.842%	$222.9176	$222.92	$222.90	$222.90
7 purchase totals =	$791.28		$843.5313	$843.54	$843.45	$843.50