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	$55.84	6.434%	$59.4327	$59.43	$59.45	$59.40
Purchase #2	$9.95	6.383%	$10.5851	$10.59	$10.60	$10.60
Purchase #3	$5.89	7.683%	$6.3425	$6.34	$6.35	$6.30
Purchase #4	$160.40	4.410%	$167.4736	$167.47	$167.45	$167.50
Purchase #5	$92.60	6.300%	$98.4338	$98.43	$98.45	$98.40
Purchase #6	$14.95	5.429%	$15.7616	$15.76	$15.75	$15.80
Purchase #7	$52.86	13.612%	$60.0553	$60.06	$60.05	$60.10
7 purchase totals =	$392.49		$418.0846	$418.08	$418.10	$418.10