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	$126.39	4.545%	$132.1344	$132.13	$132.15	$132.10
Purchase #2	$240.98	10.796%	$266.9962	$267.00	$267.00	$267.00
Purchase #3	$19.32	11.519%	$21.5455	$21.55	$21.55	$21.50
Purchase #4	$197.72	6.121%	$209.8224	$209.82	$209.80	$209.80
Purchase #5	$240.30	11.547%	$268.0474	$268.05	$268.05	$268.00
Purchase #6	$136.62	3.443%	$141.3238	$141.32	$141.30	$141.30
Purchase #7	$37.78	7.467%	$40.601	$40.60	$40.60	$40.60
7 purchase totals =	$999.11		$1,080.4707	$1,080.47	$1,080.45	$1,080.30