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	$74.54	9.444%	$81.5796	$81.58	$81.60	$81.60
Purchase #2	$9.45	8.574%	$10.2602	$10.26	$10.25	$10.30
Purchase #3	$89.29	11.734%	$99.7673	$99.77	$99.75	$99.80
Purchase #4	$110.81	7.332%	$118.9346	$118.93	$118.95	$118.90
Purchase #5	$212.67	3.779%	$220.7068	$220.71	$220.70	$220.70
Purchase #6	$51.80	3.428%	$53.5757	$53.58	$53.60	$53.60
Purchase #7	$70.93	10.745%	$78.5514	$78.55	$78.55	$78.60
7 purchase totals =	$619.49		$663.3756	$663.38	$663.40	$663.50