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	$203.28	5.479%	$214.4177	$214.42	$214.40	$214.40
Purchase #2	$172.30	8.225%	$186.4717	$186.47	$186.45	$186.50
Purchase #3	$62.72	7.552%	$67.4566	$67.46	$67.45	$67.50
Purchase #4	$64.75	4.603%	$67.7304	$67.73	$67.75	$67.70
Purchase #5	$200.28	10.547%	$221.4035	$221.40	$221.40	$221.40
Purchase #6	$27.60	7.687%	$29.7216	$29.72	$29.70	$29.70
Purchase #7	$81.26	11.867%	$90.9031	$90.90	$90.90	$90.90
7 purchase totals =	$812.19		$878.1046	$878.10	$878.05	$878.10