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	$215.97	6.857%	$230.7791	$230.78	$230.80	$230.80
Purchase #2	$24.72	12.478%	$27.8046	$27.80	$27.80	$27.80
Purchase #3	$145.87	7.303%	$156.5229	$156.52	$156.50	$156.50
Purchase #4	$115.31	11.747%	$128.8555	$128.86	$128.85	$128.90
Purchase #5	$102.54	10.759%	$113.5723	$113.57	$113.55	$113.60
Purchase #6	$195.85	13.837%	$222.9498	$222.95	$222.95	$222.90
Purchase #7	$125.83	5.568%	$132.8362	$132.84	$132.85	$132.80
7 purchase totals =	$926.09		$1,013.3204	$1,013.32	$1,013.30	$1,013.30