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	$146.28	6.563%	$155.8804	$155.88	$155.90	$155.90
Purchase #2	$64.89	5.329%	$68.348	$68.35	$68.35	$68.30
Purchase #3	$207.81	10.115%	$228.83	$228.83	$228.85	$228.80
Purchase #4	$78.80	11.742%	$88.0527	$88.05	$88.05	$88.10
Purchase #5	$90.71	10.551%	$100.2808	$100.28	$100.30	$100.30
Purchase #6	$91.32	9.357%	$99.8648	$99.86	$99.85	$99.90
Purchase #7	$192.33	8.235%	$208.1684	$208.17	$208.15	$208.20
7 purchase totals =	$872.14		$949.4251	$949.42	$949.45	$949.50