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	$108.57	9.157%	$118.5118	$118.51	$118.50	$118.50
Purchase #2	$70.53	9.359%	$77.1309	$77.13	$77.15	$77.10
Purchase #3	$83.85	6.451%	$89.2592	$89.26	$89.25	$89.30
Purchase #4	$248.41	11.745%	$277.5858	$277.59	$277.60	$277.60
Purchase #5	$69.88	3.103%	$72.0484	$72.05	$72.05	$72.00
Purchase #6	$78.57	8.522%	$85.2657	$85.27	$85.25	$85.30
Purchase #7	$38.27	10.566%	$42.3136	$42.31	$42.30	$42.30
7 purchase totals =	$698.08		$762.1154	$762.12	$762.10	$762.10