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	$180.86	13.596%	$205.4497	$205.45	$205.45	$205.40
Purchase #2	$10.55	4.178%	$10.9908	$10.99	$11.00	$11.00
Purchase #3	$207.46	3.112%	$213.9162	$213.92	$213.90	$213.90
Purchase #4	$82.31	10.328%	$90.811	$90.81	$90.80	$90.80
Purchase #5	$244.25	11.560%	$272.4853	$272.49	$272.50	$272.50
Purchase #6	$116.65	13.591%	$132.5039	$132.50	$132.50	$132.50
Purchase #7	$144.33	12.668%	$162.6137	$162.61	$162.60	$162.60
7 purchase totals =	$986.41		$1,088.7706	$1,088.77	$1,088.75	$1,088.70