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	$238.61	4.187%	$248.6006	$248.60	$248.60	$248.60
Purchase #2	$223.65	4.547%	$233.8194	$233.82	$233.80	$233.80
Purchase #3	$132.78	8.817%	$144.4872	$144.49	$144.50	$144.50
Purchase #4	$81.67	10.152%	$89.9611	$89.96	$89.95	$90.00
Purchase #5	$212.29	9.564%	$232.5934	$232.59	$232.60	$232.60
Purchase #6	$176.93	13.172%	$200.2352	$200.24	$200.25	$200.20
Purchase #7	$43.81	3.193%	$45.2089	$45.21	$45.20	$45.20
7 purchase totals =	$1,109.74		$1,194.9058	$1,194.91	$1,194.90	$1,194.90