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	$181.41	9.474%	$198.5968	$198.60	$198.60	$198.60
Purchase #2	$66.55	13.265%	$75.3779	$75.38	$75.40	$75.40
Purchase #3	$160.83	11.307%	$179.015	$179.02	$179.00	$179.00
Purchase #4	$38.52	13.215%	$43.6104	$43.61	$43.60	$43.60
Purchase #5	$244.62	5.723%	$258.6196	$258.62	$258.60	$258.60
Purchase #6	$145.49	8.826%	$158.3309	$158.33	$158.35	$158.30
Purchase #7	$118.31	11.870%	$132.3534	$132.35	$132.35	$132.40
7 purchase totals =	$955.73		$1,045.9040	$1,045.91	$1,045.90	$1,045.90