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	$130.66	10.499%	$144.378	$144.38	$144.40	$144.40
Purchase #2	$155.80	5.756%	$164.7678	$164.77	$164.75	$164.80
Purchase #3	$157.34	7.304%	$168.8321	$168.83	$168.85	$168.80
Purchase #4	$90.43	10.387%	$99.823	$99.82	$99.80	$99.80
Purchase #5	$120.81	10.462%	$133.4491	$133.45	$133.45	$133.40
Purchase #6	$248.39	5.558%	$262.1955	$262.20	$262.20	$262.20
Purchase #7	$96.76	8.730%	$105.2071	$105.21	$105.20	$105.20
7 purchase totals =	$1,000.19		$1,078.6526	$1,078.66	$1,078.65	$1,078.60