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	$183.80	9.136%	$200.592	$200.59	$200.60	$200.60
Purchase #2	$205.93	6.477%	$219.2681	$219.27	$219.25	$219.30
Purchase #3	$184.43	6.321%	$196.0878	$196.09	$196.10	$196.10
Purchase #4	$174.34	11.707%	$194.75	$194.75	$194.75	$194.80
Purchase #5	$30.31	6.737%	$32.352	$32.35	$32.35	$32.40
Purchase #6	$235.41	4.645%	$246.3448	$246.34	$246.35	$246.30
Purchase #7	$27.91	4.103%	$29.0551	$29.06	$29.05	$29.10
7 purchase totals =	$1,042.13		$1,118.4498	$1,118.45	$1,118.45	$1,118.60