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	$131.41	9.293%	$143.6219	$143.62	$143.60	$143.60
Purchase #2	$152.81	9.123%	$166.7509	$166.75	$166.75	$166.80
Purchase #3	$105.27	9.689%	$115.4696	$115.47	$115.45	$115.50
Purchase #4	$102.67	9.466%	$112.3887	$112.39	$112.40	$112.40
Purchase #5	$55.67	3.229%	$57.4676	$57.47	$57.45	$57.50
Purchase #6	$108.48	3.244%	$111.9991	$112.00	$112.00	$112.00
Purchase #7	$166.60	5.413%	$175.6181	$175.62	$175.60	$175.60
7 purchase totals =	$822.91		$883.3159	$883.32	$883.25	$883.40