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	$153.75	12.278%	$172.6274	$172.63	$172.65	$172.60
Purchase #2	$26.81	5.835%	$28.3744	$28.37	$28.35	$28.40
Purchase #3	$190.39	12.871%	$214.8951	$214.90	$214.90	$214.90
Purchase #4	$220.86	9.437%	$241.7026	$241.70	$241.70	$241.70
Purchase #5	$106.71	12.246%	$119.7777	$119.78	$119.80	$119.80
Purchase #6	$6.56	7.104%	$7.026	$7.03	$7.05	$7.00
Purchase #7	$205.71	8.152%	$222.4795	$222.48	$222.50	$222.50
7 purchase totals =	$910.79		$1,006.8827	$1,006.89	$1,006.95	$1,006.90