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	$31.43	12.586%	$35.3858	$35.39	$35.40	$35.40
Purchase #2	$158.62	6.234%	$168.5084	$168.51	$168.50	$168.50
Purchase #3	$187.97	3.254%	$194.0865	$194.09	$194.10	$194.10
Purchase #4	$48.31	7.573%	$51.9685	$51.97	$51.95	$52.00
Purchase #5	$13.45	7.179%	$14.4156	$14.42	$14.40	$14.40
Purchase #6	$73.89	6.756%	$78.882	$78.88	$78.90	$78.90
Purchase #7	$170.87	9.656%	$187.3692	$187.37	$187.35	$187.40
7 purchase totals =	$684.54		$730.6160	$730.63	$730.60	$730.70