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	$71.84	8.765%	$78.1368	$78.14	$78.15	$78.10
Purchase #2	$100.40	10.635%	$111.0775	$111.08	$111.10	$111.10
Purchase #3	$86.81	11.184%	$96.5188	$96.52	$96.50	$96.50
Purchase #4	$166.71	10.329%	$183.9295	$183.93	$183.95	$183.90
Purchase #5	$190.73	10.523%	$210.8005	$210.80	$210.80	$210.80
Purchase #6	$199.64	7.615%	$214.8426	$214.84	$214.85	$214.80
Purchase #7	$142.36	6.241%	$151.2447	$151.24	$151.25	$151.20
7 purchase totals =	$958.49		$1,046.5504	$1,046.55	$1,046.60	$1,046.40