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	$182.54	9.291%	$199.4998	$199.50	$199.50	$199.50
Purchase #2	$136.83	10.451%	$151.1301	$151.13	$151.15	$151.10
Purchase #3	$62.89	3.466%	$65.0698	$65.07	$65.05	$65.10
Purchase #4	$139.59	9.635%	$153.0395	$153.04	$153.05	$153.00
Purchase #5	$160.58	10.506%	$177.4505	$177.45	$177.45	$177.50
Purchase #6	$70.30	12.707%	$79.233	$79.23	$79.25	$79.20
Purchase #7	$161.57	6.390%	$171.8943	$171.89	$171.90	$171.90
7 purchase totals =	$914.30		$997.3170	$997.31	$997.35	$997.30