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	$158.45	6.331%	$168.4815	$168.48	$168.50	$168.50
Purchase #2	$112.85	9.809%	$123.9195	$123.92	$123.90	$123.90
Purchase #3	$118.67	11.652%	$132.4974	$132.50	$132.50	$132.50
Purchase #4	$180.35	10.785%	$199.8007	$199.80	$199.80	$199.80
Purchase #5	$147.41	3.113%	$151.9989	$152.00	$152.00	$152.00
Purchase #6	$145.42	3.296%	$150.213	$150.21	$150.20	$150.20
Purchase #7	$161.68	6.729%	$172.5594	$172.56	$172.55	$172.60
7 purchase totals =	$1,024.83		$1,099.4704	$1,099.47	$1,099.45	$1,099.50