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	$11.71	13.493%	$13.29	$13.29	$13.30	$13.30
Purchase #2	$21.95	11.462%	$24.4659	$24.47	$24.45	$24.50
Purchase #3	$94.45	6.848%	$100.9179	$100.92	$100.90	$100.90
Purchase #4	$82.81	5.276%	$87.1791	$87.18	$87.20	$87.20
Purchase #5	$192.54	8.337%	$208.5921	$208.59	$208.60	$208.60
Purchase #6	$115.56	10.525%	$127.7227	$127.72	$127.70	$127.70
Purchase #7	$164.93	3.830%	$171.2468	$171.25	$171.25	$171.20
7 purchase totals =	$683.95		$733.4145	$733.42	$733.40	$733.40