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	$112.47	13.147%	$127.2564	$127.26	$127.25	$127.30
Purchase #2	$97.31	5.867%	$103.0192	$103.02	$103.00	$103.00
Purchase #3	$68.95	7.293%	$73.9785	$73.98	$74.00	$74.00
Purchase #4	$25.60	9.205%	$27.9565	$27.96	$27.95	$28.00
Purchase #5	$169.50	11.157%	$188.4111	$188.41	$188.40	$188.40
Purchase #6	$68.37	12.774%	$77.1036	$77.10	$77.10	$77.10
Purchase #7	$113.27	12.209%	$127.0991	$127.10	$127.10	$127.10
7 purchase totals =	$655.47		$724.8244	$724.83	$724.80	$724.90