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	$224.49	9.357%	$245.4955	$245.50	$245.50	$245.50
Purchase #2	$175.40	8.331%	$190.0126	$190.01	$190.00	$190.00
Purchase #3	$100.56	12.208%	$112.8364	$112.84	$112.85	$112.80
Purchase #4	$19.56	5.389%	$20.6141	$20.61	$20.60	$20.60
Purchase #5	$11.95	13.401%	$13.5514	$13.55	$13.55	$13.60
Purchase #6	$164.89	9.327%	$180.2693	$180.27	$180.25	$180.30
Purchase #7	$84.38	11.864%	$94.3908	$94.39	$94.40	$94.40
7 purchase totals =	$781.23		$857.1701	$857.17	$857.15	$857.20