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	$214.90	3.131%	$221.6285	$221.63	$221.65	$221.60
Purchase #2	$58.59	12.573%	$65.9565	$65.96	$65.95	$66.00
Purchase #3	$73.98	5.660%	$78.1673	$78.17	$78.15	$78.20
Purchase #4	$70.57	11.672%	$78.8069	$78.81	$78.80	$78.80
Purchase #5	$196.95	8.545%	$213.7794	$213.78	$213.80	$213.80
Purchase #6	$31.58	11.114%	$35.0898	$35.09	$35.10	$35.10
Purchase #7	$67.99	3.192%	$70.1602	$70.16	$70.15	$70.20
7 purchase totals =	$714.56		$763.5886	$763.60	$763.60	$763.70