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	$69.66	6.378%	$74.1029	$74.10	$74.10	$74.10
Purchase #2	$178.51	10.247%	$196.8019	$196.80	$196.80	$196.80
Purchase #3	$209.39	3.228%	$216.1491	$216.15	$216.15	$216.10
Purchase #4	$192.95	8.304%	$208.9726	$208.97	$208.95	$209.00
Purchase #5	$143.66	13.216%	$162.6461	$162.65	$162.65	$162.60
Purchase #6	$63.32	11.493%	$70.5974	$70.60	$70.60	$70.60
Purchase #7	$82.47	9.257%	$90.1042	$90.10	$90.10	$90.10
7 purchase totals =	$939.96		$1,019.3742	$1,019.37	$1,019.35	$1,019.30