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	$34.38	3.601%	$35.618	$35.62	$35.60	$35.60
Purchase #2	$71.93	9.651%	$78.872	$78.87	$78.85	$78.90
Purchase #3	$178.39	10.344%	$196.8427	$196.84	$196.85	$196.80
Purchase #4	$72.96	10.255%	$80.442	$80.44	$80.45	$80.40
Purchase #5	$136.98	11.703%	$153.0108	$153.01	$153.00	$153.00
Purchase #6	$235.95	10.141%	$259.8777	$259.88	$259.90	$259.90
Purchase #7	$225.43	10.850%	$249.8892	$249.89	$249.90	$249.90
7 purchase totals =	$956.02		$1,054.5524	$1,054.55	$1,054.55	$1,054.50