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	$138.50	7.493%	$148.8778	$148.88	$148.90	$148.90
Purchase #2	$137.49	9.472%	$150.5131	$150.51	$150.50	$150.50
Purchase #3	$207.51	8.721%	$225.6069	$225.61	$225.60	$225.60
Purchase #4	$94.67	4.196%	$98.6424	$98.64	$98.65	$98.60
Purchase #5	$240.34	4.656%	$251.5302	$251.53	$251.55	$251.50
Purchase #6	$147.64	7.529%	$158.7558	$158.76	$158.75	$158.80
Purchase #7	$31.38	13.190%	$35.519	$35.52	$35.50	$35.50
7 purchase totals =	$997.53		$1,069.4452	$1,069.45	$1,069.45	$1,069.40