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	$214.75	13.405%	$243.5372	$243.54	$243.55	$243.50
Purchase #2	$125.52	3.260%	$129.612	$129.61	$129.60	$129.60
Purchase #3	$105.88	4.845%	$111.0099	$111.01	$111.00	$111.00
Purchase #4	$204.86	13.118%	$231.7335	$231.73	$231.75	$231.70
Purchase #5	$225.45	13.274%	$255.3762	$255.38	$255.40	$255.40
Purchase #6	$148.87	11.803%	$166.4411	$166.44	$166.45	$166.40
Purchase #7	$46.89	10.592%	$51.8566	$51.86	$51.85	$51.90
7 purchase totals =	$1,072.22		$1,189.5665	$1,189.57	$1,189.60	$1,189.50