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	$136.26	6.820%	$145.5529	$145.55	$145.55	$145.60
Purchase #2	$68.55	7.672%	$73.8092	$73.81	$73.80	$73.80
Purchase #3	$130.51	11.205%	$145.1336	$145.13	$145.15	$145.10
Purchase #4	$100.25	3.357%	$103.6154	$103.62	$103.60	$103.60
Purchase #5	$41.75	9.860%	$45.8666	$45.87	$45.85	$45.90
Purchase #6	$116.69	6.420%	$124.1815	$124.18	$124.20	$124.20
Purchase #7	$115.68	10.565%	$127.9016	$127.90	$127.90	$127.90
7 purchase totals =	$709.69		$766.0608	$766.06	$766.05	$766.10