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	$54.31	4.716%	$56.8713	$56.87	$56.85	$56.90
Purchase #2	$29.38	8.291%	$31.8159	$31.82	$31.80	$31.80
Purchase #3	$81.87	4.214%	$85.32	$85.32	$85.30	$85.30
Purchase #4	$159.72	7.391%	$171.5249	$171.52	$171.50	$171.50
Purchase #5	$22.30	9.578%	$24.4359	$24.44	$24.45	$24.40
Purchase #6	$119.70	6.134%	$127.0424	$127.04	$127.05	$127.00
Purchase #7	$202.54	4.429%	$211.5105	$211.51	$211.50	$211.50
7 purchase totals =	$669.82		$708.5209	$708.52	$708.45	$708.40