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	$69.80	3.345%	$72.1348	$72.13	$72.15	$72.10
Purchase #2	$221.51	7.817%	$238.8254	$238.83	$238.85	$238.80
Purchase #3	$37.88	10.738%	$41.9476	$41.95	$41.95	$41.90
Purchase #4	$62.50	4.486%	$65.3038	$65.30	$65.30	$65.30
Purchase #5	$99.89	8.379%	$108.2598	$108.26	$108.25	$108.30
Purchase #6	$166.32	6.401%	$176.9661	$176.97	$176.95	$177.00
Purchase #7	$233.76	9.200%	$255.2659	$255.27	$255.25	$255.30
7 purchase totals =	$891.66		$958.7034	$958.71	$958.70	$958.70