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	$186.92	9.789%	$205.2176	$205.22	$205.20	$205.20
Purchase #2	$30.66	12.395%	$34.4603	$34.46	$34.45	$34.50
Purchase #3	$10.41	3.612%	$10.786	$10.79	$10.80	$10.80
Purchase #4	$52.57	6.296%	$55.8798	$55.88	$55.90	$55.90
Purchase #5	$144.69	13.393%	$164.0683	$164.07	$164.05	$164.10
Purchase #6	$210.89	7.851%	$227.447	$227.45	$227.45	$227.40
Purchase #7	$213.42	5.136%	$224.3813	$224.38	$224.40	$224.40
7 purchase totals =	$849.56		$922.2403	$922.25	$922.25	$922.30