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	$58.87	10.486%	$65.0431	$65.04	$65.05	$65.00
Purchase #2	$108.89	3.405%	$112.5977	$112.60	$112.60	$112.60
Purchase #3	$97.80	5.777%	$103.4499	$103.45	$103.45	$103.40
Purchase #4	$151.86	8.811%	$165.2404	$165.24	$165.25	$165.20
Purchase #5	$159.39	4.463%	$166.5036	$166.50	$166.50	$166.50
Purchase #6	$58.73	7.826%	$63.3262	$63.33	$63.35	$63.30
Purchase #7	$140.82	5.534%	$148.613	$148.61	$148.60	$148.60
7 purchase totals =	$776.36		$824.7739	$824.77	$824.80	$824.60