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	$107.77	3.344%	$111.3738	$111.37	$111.35	$111.40
Purchase #2	$238.73	12.182%	$267.8121	$267.81	$267.80	$267.80
Purchase #3	$160.55	3.758%	$166.5835	$166.58	$166.60	$166.60
Purchase #4	$38.91	10.391%	$42.9531	$42.95	$42.95	$43.00
Purchase #5	$45.37	5.182%	$47.7211	$47.72	$47.70	$47.70
Purchase #6	$154.34	9.205%	$168.547	$168.55	$168.55	$168.50
Purchase #7	$83.76	10.498%	$92.5531	$92.55	$92.55	$92.60
7 purchase totals =	$829.43		$897.5437	$897.53	$897.50	$897.60