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	$96.61	13.379%	$109.5355	$109.54	$109.55	$109.50
Purchase #2	$94.40	10.595%	$104.4017	$104.40	$104.40	$104.40
Purchase #3	$32.60	10.115%	$35.8975	$35.90	$35.90	$35.90
Purchase #4	$21.59	5.315%	$22.7375	$22.74	$22.75	$22.70
Purchase #5	$105.30	10.665%	$116.5302	$116.53	$116.55	$116.50
Purchase #6	$157.25	6.570%	$167.5813	$167.58	$167.60	$167.60
Purchase #7	$160.35	6.523%	$170.8096	$170.81	$170.80	$170.80
7 purchase totals =	$668.10		$727.4933	$727.50	$727.55	$727.40