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	$224.58	11.687%	$250.8267	$250.83	$250.85	$250.80
Purchase #2	$231.33	12.201%	$259.5546	$259.55	$259.55	$259.60
Purchase #3	$198.77	11.539%	$221.7061	$221.71	$221.70	$221.70
Purchase #4	$172.51	3.693%	$178.8808	$178.88	$178.90	$178.90
Purchase #5	$12.45	6.612%	$13.2732	$13.27	$13.25	$13.30
Purchase #6	$14.50	7.606%	$15.6029	$15.60	$15.60	$15.60
Purchase #7	$76.87	8.527%	$83.4247	$83.42	$83.40	$83.40
7 purchase totals =	$931.01		$1,023.2690	$1,023.26	$1,023.25	$1,023.30