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	$17.76	4.786%	$18.61	$18.61	$18.60	$18.60
Purchase #2	$95.27	8.524%	$103.3908	$103.39	$103.40	$103.40
Purchase #3	$94.91	9.287%	$103.7243	$103.72	$103.70	$103.70
Purchase #4	$205.50	13.418%	$233.074	$233.07	$233.05	$233.10
Purchase #5	$195.73	11.276%	$217.8005	$217.80	$217.80	$217.80
Purchase #6	$117.68	12.190%	$132.0252	$132.03	$132.05	$132.00
Purchase #7	$247.76	4.309%	$258.436	$258.44	$258.45	$258.40
7 purchase totals =	$974.61		$1,067.0608	$1,067.06	$1,067.05	$1,067.00