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	$214.75	13.571%	$243.8937	$243.89	$243.90	$243.90
Purchase #2	$92.31	4.462%	$96.4289	$96.43	$96.45	$96.40
Purchase #3	$103.55	6.416%	$110.1938	$110.19	$110.20	$110.20
Purchase #4	$123.38	3.167%	$127.2874	$127.29	$127.30	$127.30
Purchase #5	$69.98	12.304%	$78.5903	$78.59	$78.60	$78.60
Purchase #6	$14.40	9.844%	$15.8175	$15.82	$15.80	$15.80
Purchase #7	$193.95	5.857%	$205.3097	$205.31	$205.30	$205.30
7 purchase totals =	$812.32		$877.5213	$877.52	$877.55	$877.50