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	$233.83	7.193%	$250.6494	$250.65	$250.65	$250.60
Purchase #2	$163.94	5.145%	$172.3747	$172.37	$172.35	$172.40
Purchase #3	$180.45	7.223%	$193.4839	$193.48	$193.50	$193.50
Purchase #4	$50.72	10.556%	$56.074	$56.07	$56.05	$56.10
Purchase #5	$152.98	12.175%	$171.6053	$171.61	$171.60	$171.60
Purchase #6	$114.59	7.717%	$123.4329	$123.43	$123.45	$123.40
Purchase #7	$185.58	7.456%	$199.4168	$199.42	$199.40	$199.40
7 purchase totals =	$1,082.09		$1,167.0370	$1,167.03	$1,167.00	$1,167.00