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	$87.82	10.167%	$96.7487	$96.75	$96.75	$96.70
Purchase #2	$101.52	7.537%	$109.1716	$109.17	$109.15	$109.20
Purchase #3	$204.28	11.552%	$227.8784	$227.88	$227.90	$227.90
Purchase #4	$71.98	9.166%	$78.5777	$78.58	$78.60	$78.60
Purchase #5	$95.58	4.370%	$99.7568	$99.76	$99.75	$99.80
Purchase #6	$68.67	9.350%	$75.0906	$75.09	$75.10	$75.10
Purchase #7	$11.98	10.235%	$13.2062	$13.21	$13.20	$13.20
7 purchase totals =	$641.83		$700.4300	$700.44	$700.45	$700.50