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	$218.67	10.268%	$241.123	$241.12	$241.10	$241.10
Purchase #2	$85.48	13.402%	$96.936	$96.94	$96.95	$96.90
Purchase #3	$96.60	9.153%	$105.4418	$105.44	$105.45	$105.40
Purchase #4	$159.97	5.375%	$168.5684	$168.57	$168.55	$168.60
Purchase #5	$14.87	4.376%	$15.5207	$15.52	$15.50	$15.50
Purchase #6	$103.32	10.799%	$114.4775	$114.48	$114.50	$114.50
Purchase #7	$225.64	13.301%	$255.6524	$255.65	$255.65	$255.70
7 purchase totals =	$904.55		$997.7198	$997.72	$997.70	$997.70