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	$141.65	9.449%	$155.0345	$155.03	$155.05	$155.00
Purchase #2	$39.39	7.865%	$42.488	$42.49	$42.50	$42.50
Purchase #3	$192.70	6.312%	$204.8632	$204.86	$204.85	$204.90
Purchase #4	$43.82	5.589%	$46.2691	$46.27	$46.25	$46.30
Purchase #5	$68.43	8.243%	$74.0707	$74.07	$74.05	$74.10
Purchase #6	$174.94	12.301%	$196.4594	$196.46	$196.45	$196.50
Purchase #7	$162.29	8.725%	$176.4498	$176.45	$176.45	$176.40
7 purchase totals =	$823.22		$895.6347	$895.63	$895.60	$895.70