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	$116.86	9.429%	$127.8787	$127.88	$127.90	$127.90
Purchase #2	$137.29	5.327%	$144.6034	$144.60	$144.60	$144.60
Purchase #3	$63.82	13.360%	$72.3464	$72.35	$72.35	$72.30
Purchase #4	$18.83	9.819%	$20.6789	$20.68	$20.70	$20.70
Purchase #5	$169.67	9.745%	$186.2043	$186.20	$186.20	$186.20
Purchase #6	$169.42	8.556%	$183.9156	$183.92	$183.90	$183.90
Purchase #7	$135.37	11.531%	$150.9795	$150.98	$151.00	$151.00
7 purchase totals =	$811.26		$886.6068	$886.61	$886.65	$886.60