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	$75.53	7.857%	$81.4644	$81.46	$81.45	$81.50
Purchase #2	$72.87	10.354%	$80.415	$80.42	$80.40	$80.40
Purchase #3	$14.53	11.147%	$16.1497	$16.15	$16.15	$16.10
Purchase #4	$96.27	4.452%	$100.5559	$100.56	$100.55	$100.60
Purchase #5	$132.78	9.632%	$145.5694	$145.57	$145.55	$145.60
Purchase #6	$84.72	8.264%	$91.7213	$91.72	$91.70	$91.70
Purchase #7	$160.55	13.417%	$182.091	$182.09	$182.10	$182.10
7 purchase totals =	$637.25		$697.9667	$697.97	$697.90	$698.00