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	$38.71	6.296%	$41.1472	$41.15	$41.15	$41.10
Purchase #2	$60.32	4.312%	$62.921	$62.92	$62.90	$62.90
Purchase #3	$153.79	3.452%	$159.0988	$159.10	$159.10	$159.10
Purchase #4	$97.81	5.745%	$103.4292	$103.43	$103.45	$103.40
Purchase #5	$104.58	6.413%	$111.2867	$111.29	$111.30	$111.30
Purchase #6	$154.86	6.405%	$164.7788	$164.78	$164.80	$164.80
Purchase #7	$132.52	5.190%	$139.3978	$139.40	$139.40	$139.40
7 purchase totals =	$742.59		$782.0595	$782.07	$782.10	$782.00