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	$96.38	10.546%	$106.5442	$106.54	$106.55	$106.50
Purchase #2	$92.43	8.862%	$100.6211	$100.62	$100.60	$100.60
Purchase #3	$12.81	5.611%	$13.5288	$13.53	$13.55	$13.50
Purchase #4	$84.47	12.631%	$95.1394	$95.14	$95.15	$95.10
Purchase #5	$104.27	11.327%	$116.0807	$116.08	$116.10	$116.10
Purchase #6	$232.99	12.398%	$261.8761	$261.88	$261.90	$261.90
Purchase #7	$18.44	11.645%	$20.5873	$20.59	$20.60	$20.60
7 purchase totals =	$641.79		$714.3776	$714.38	$714.45	$714.30