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	$78.94	10.379%	$87.1332	$87.13	$87.15	$87.10
Purchase #2	$166.44	8.648%	$180.8337	$180.83	$180.85	$180.80
Purchase #3	$67.48	6.849%	$72.1017	$72.10	$72.10	$72.10
Purchase #4	$87.91	13.724%	$99.9748	$99.97	$99.95	$100.00
Purchase #5	$90.30	6.798%	$96.4386	$96.44	$96.45	$96.40
Purchase #6	$52.84	3.377%	$54.6244	$54.62	$54.60	$54.60
Purchase #7	$34.84	4.534%	$36.4196	$36.42	$36.40	$36.40
7 purchase totals =	$578.75		$627.5260	$627.51	$627.50	$627.40