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	$108.92	9.489%	$119.2554	$119.26	$119.25	$119.30
Purchase #2	$78.93	12.866%	$89.0851	$89.09	$89.10	$89.10
Purchase #3	$73.44	10.447%	$81.1123	$81.11	$81.10	$81.10
Purchase #4	$144.45	13.748%	$164.309	$164.31	$164.30	$164.30
Purchase #5	$129.25	13.674%	$146.9236	$146.92	$146.90	$146.90
Purchase #6	$149.45	9.733%	$163.996	$164.00	$164.00	$164.00
Purchase #7	$160.95	4.135%	$167.6053	$167.61	$167.60	$167.60
7 purchase totals =	$845.39		$932.2867	$932.30	$932.25	$932.30