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	$138.37	7.273%	$148.4337	$148.43	$148.45	$148.40
Purchase #2	$172.87	4.371%	$180.4261	$180.43	$180.45	$180.40
Purchase #3	$81.88	10.434%	$90.4234	$90.42	$90.40	$90.40
Purchase #4	$104.77	8.406%	$113.577	$113.58	$113.60	$113.60
Purchase #5	$207.96	7.244%	$223.0246	$223.02	$223.00	$223.00
Purchase #6	$185.75	5.754%	$196.4381	$196.44	$196.45	$196.40
Purchase #7	$113.71	11.367%	$126.6354	$126.64	$126.65	$126.60
7 purchase totals =	$1,005.31		$1,078.9583	$1,078.96	$1,079.00	$1,078.80