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	$94.81	13.601%	$107.7051	$107.71	$107.70	$107.70
Purchase #2	$32.81	13.357%	$37.1924	$37.19	$37.20	$37.20
Purchase #3	$17.50	9.548%	$19.1709	$19.17	$19.15	$19.20
Purchase #4	$241.43	13.726%	$274.5687	$274.57	$274.55	$274.60
Purchase #5	$45.37	12.321%	$50.96	$50.96	$50.95	$51.00
Purchase #6	$28.36	10.599%	$31.3659	$31.37	$31.35	$31.40
Purchase #7	$38.88	12.119%	$43.5919	$43.59	$43.60	$43.60
7 purchase totals =	$499.16		$564.5549	$564.56	$564.50	$564.70