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	$130.43	9.152%	$142.367	$142.37	$142.35	$142.40
Purchase #2	$90.64	5.182%	$95.337	$95.34	$95.35	$95.30
Purchase #3	$153.25	10.178%	$168.8478	$168.85	$168.85	$168.80
Purchase #4	$65.86	10.838%	$72.9979	$73.00	$73.00	$73.00
Purchase #5	$27.89	11.211%	$31.0167	$31.02	$31.00	$31.00
Purchase #6	$18.72	11.203%	$20.8172	$20.82	$20.80	$20.80
Purchase #7	$95.69	10.629%	$105.8609	$105.86	$105.85	$105.90
7 purchase totals =	$582.48		$637.2445	$637.26	$637.20	$637.20