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	$192.92	6.314%	$205.101	$205.10	$205.10	$205.10
Purchase #2	$166.89	13.598%	$189.5837	$189.58	$189.60	$189.60
Purchase #3	$248.88	6.602%	$265.3111	$265.31	$265.30	$265.30
Purchase #4	$136.36	10.600%	$150.8142	$150.81	$150.80	$150.80
Purchase #5	$90.80	3.837%	$94.284	$94.28	$94.30	$94.30
Purchase #6	$139.94	9.235%	$152.8635	$152.86	$152.85	$152.90
Purchase #7	$117.71	8.258%	$127.4305	$127.43	$127.45	$127.40
7 purchase totals =	$1,093.50		$1,185.3880	$1,185.37	$1,185.40	$1,185.40