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	$202.85	11.129%	$225.4252	$225.43	$225.45	$225.40
Purchase #2	$122.54	3.312%	$126.5985	$126.60	$126.60	$126.60
Purchase #3	$233.56	13.403%	$264.864	$264.86	$264.85	$264.90
Purchase #4	$71.47	11.353%	$79.584	$79.58	$79.60	$79.60
Purchase #5	$186.95	5.481%	$197.1967	$197.20	$197.20	$197.20
Purchase #6	$89.53	13.340%	$101.4733	$101.47	$101.45	$101.50
Purchase #7	$99.68	5.233%	$104.8963	$104.90	$104.90	$104.90
7 purchase totals =	$1,006.58		$1,100.0380	$1,100.04	$1,100.05	$1,100.10