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	$118.46	4.197%	$123.4318	$123.43	$123.45	$123.40
Purchase #2	$153.98	3.821%	$159.8636	$159.86	$159.85	$159.90
Purchase #3	$88.85	10.236%	$97.9447	$97.94	$97.95	$97.90
Purchase #4	$100.84	10.127%	$111.0521	$111.05	$111.05	$111.10
Purchase #5	$65.46	8.244%	$70.8565	$70.86	$70.85	$70.90
Purchase #6	$179.61	8.197%	$194.3326	$194.33	$194.35	$194.30
Purchase #7	$38.32	6.867%	$40.9514	$40.95	$40.95	$41.00
7 purchase totals =	$745.52		$798.4327	$798.42	$798.45	$798.50