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	$168.42	7.145%	$180.4536	$180.45	$180.45	$180.50
Purchase #2	$32.46	12.206%	$36.4221	$36.42	$36.40	$36.40
Purchase #3	$43.88	7.232%	$47.0534	$47.05	$47.05	$47.10
Purchase #4	$154.25	12.752%	$173.92	$173.92	$173.90	$173.90
Purchase #5	$18.37	13.801%	$20.9052	$20.91	$20.90	$20.90
Purchase #6	$98.71	5.816%	$104.451	$104.45	$104.45	$104.50
Purchase #7	$132.90	11.800%	$148.5822	$148.58	$148.60	$148.60
7 purchase totals =	$648.99		$711.7875	$711.78	$711.75	$711.90