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	$127.41	5.524%	$134.4481	$134.45	$134.45	$134.40
Purchase #2	$86.75	11.719%	$96.9162	$96.92	$96.90	$96.90
Purchase #3	$227.93	5.770%	$241.0816	$241.08	$241.10	$241.10
Purchase #4	$112.39	4.107%	$117.0059	$117.01	$117.00	$117.00
Purchase #5	$197.34	5.665%	$208.5193	$208.52	$208.50	$208.50
Purchase #6	$100.54	13.670%	$114.2838	$114.28	$114.30	$114.30
Purchase #7	$80.67	12.741%	$90.9482	$90.95	$90.95	$90.90
7 purchase totals =	$933.03		$1,003.2031	$1,003.21	$1,003.20	$1,003.10