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	$216.91	4.323%	$226.287	$226.29	$226.30	$226.30
Purchase #2	$104.37	6.681%	$111.343	$111.34	$111.35	$111.30
Purchase #3	$217.32	13.691%	$247.0733	$247.07	$247.05	$247.10
Purchase #4	$127.39	5.204%	$134.0194	$134.02	$134.00	$134.00
Purchase #5	$54.39	6.491%	$57.9205	$57.92	$57.90	$57.90
Purchase #6	$36.81	9.172%	$40.1862	$40.19	$40.20	$40.20
Purchase #7	$40.96	6.259%	$43.5237	$43.52	$43.50	$43.50
7 purchase totals =	$798.15		$860.3531	$860.35	$860.30	$860.30