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	$173.94	10.692%	$192.5377	$192.54	$192.55	$192.50
Purchase #2	$48.95	12.435%	$55.0369	$55.04	$55.05	$55.00
Purchase #3	$147.54	3.314%	$152.4295	$152.43	$152.45	$152.40
Purchase #4	$223.40	11.624%	$249.368	$249.37	$249.35	$249.40
Purchase #5	$144.81	5.299%	$152.4835	$152.48	$152.50	$152.50
Purchase #6	$188.48	10.145%	$207.6013	$207.60	$207.60	$207.60
Purchase #7	$50.40	13.493%	$57.2005	$57.20	$57.20	$57.20
7 purchase totals =	$977.52		$1,066.6574	$1,066.66	$1,066.70	$1,066.60