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	$155.78	3.255%	$160.8506	$160.85	$160.85	$160.90
Purchase #2	$24.79	4.737%	$25.9643	$25.96	$25.95	$26.00
Purchase #3	$71.93	13.807%	$81.8614	$81.86	$81.85	$81.90
Purchase #4	$13.72	13.669%	$15.5954	$15.60	$15.60	$15.60
Purchase #5	$228.71	7.379%	$245.5865	$245.59	$245.60	$245.60
Purchase #6	$90.67	9.528%	$99.309	$99.31	$99.30	$99.30
Purchase #7	$52.40	9.819%	$57.5452	$57.55	$57.55	$57.50
7 purchase totals =	$638.00		$686.7124	$686.72	$686.70	$686.80