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	$63.63	3.616%	$65.9309	$65.93	$65.95	$65.90
Purchase #2	$100.60	13.454%	$114.1347	$114.13	$114.15	$114.10
Purchase #3	$121.40	9.553%	$132.9973	$133.00	$133.00	$133.00
Purchase #4	$127.96	3.288%	$132.1673	$132.17	$132.15	$132.20
Purchase #5	$148.83	12.354%	$167.2165	$167.22	$167.20	$167.20
Purchase #6	$20.80	7.839%	$22.4305	$22.43	$22.45	$22.40
Purchase #7	$142.48	6.667%	$151.9791	$151.98	$152.00	$152.00
7 purchase totals =	$725.70		$786.8563	$786.86	$786.90	$786.80