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	$197.25	4.184%	$205.5029	$205.50	$205.50	$205.50
Purchase #2	$52.94	12.639%	$59.6311	$59.63	$59.65	$59.60
Purchase #3	$153.89	3.241%	$158.8776	$158.88	$158.90	$158.90
Purchase #4	$112.42	13.457%	$127.5484	$127.55	$127.55	$127.50
Purchase #5	$228.80	9.737%	$251.0783	$251.08	$251.10	$251.10
Purchase #6	$40.49	9.204%	$44.2167	$44.22	$44.20	$44.20
Purchase #7	$192.94	7.809%	$208.0067	$208.01	$208.00	$208.00
7 purchase totals =	$978.73		$1,054.8617	$1,054.87	$1,054.90	$1,054.80