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	$107.92	6.802%	$115.2607	$115.26	$115.25	$115.30
Purchase #2	$40.26	6.856%	$43.0202	$43.02	$43.00	$43.00
Purchase #3	$209.86	6.477%	$223.4526	$223.45	$223.45	$223.50
Purchase #4	$94.44	9.689%	$103.5903	$103.59	$103.60	$103.60
Purchase #5	$33.38	4.245%	$34.797	$34.80	$34.80	$34.80
Purchase #6	$220.77	12.591%	$248.5672	$248.57	$248.55	$248.60
Purchase #7	$164.44	4.658%	$172.0996	$172.10	$172.10	$172.10
7 purchase totals =	$871.07		$940.7876	$940.79	$940.75	$940.90