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	$100.86	3.139%	$104.026	$104.03	$104.05	$104.00
Purchase #2	$181.78	3.139%	$187.4861	$187.49	$187.50	$187.50
Purchase #3	$162.77	5.727%	$172.0918	$172.09	$172.10	$172.10
Purchase #4	$218.57	4.128%	$227.5926	$227.59	$227.60	$227.60
Purchase #5	$176.79	7.522%	$190.0881	$190.09	$190.10	$190.10
Purchase #6	$73.28	7.416%	$78.7144	$78.71	$78.70	$78.70
Purchase #7	$206.54	13.538%	$234.5014	$234.50	$234.50	$234.50
7 purchase totals =	$1,120.59		$1,194.5004	$1,194.50	$1,194.55	$1,194.50