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	$97.37	12.602%	$109.6406	$109.64	$109.65	$109.60
Purchase #2	$161.99	6.546%	$172.5939	$172.59	$172.60	$172.60
Purchase #3	$139.53	8.129%	$150.8724	$150.87	$150.85	$150.90
Purchase #4	$87.54	12.652%	$98.6156	$98.62	$98.60	$98.60
Purchase #5	$119.35	12.259%	$133.9811	$133.98	$134.00	$134.00
Purchase #6	$139.27	4.510%	$145.5511	$145.55	$145.55	$145.60
Purchase #7	$143.96	12.630%	$162.1421	$162.14	$162.15	$162.10
7 purchase totals =	$889.01		$973.3968	$973.39	$973.40	$973.40