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	$210.86	4.398%	$220.1336	$220.13	$220.15	$220.10
Purchase #2	$203.77	10.334%	$224.8276	$224.83	$224.85	$224.80
Purchase #3	$191.79	6.334%	$203.938	$203.94	$203.95	$203.90
Purchase #4	$111.31	4.563%	$116.3891	$116.39	$116.40	$116.40
Purchase #5	$159.80	3.149%	$164.8321	$164.83	$164.85	$164.80
Purchase #6	$126.54	4.192%	$131.8446	$131.84	$131.85	$131.80
Purchase #7	$246.43	6.142%	$261.5657	$261.57	$261.55	$261.60
7 purchase totals =	$1,250.50		$1,323.5307	$1,323.53	$1,323.60	$1,323.40