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	$62.64	3.164%	$64.6219	$64.62	$64.60	$64.60
Purchase #2	$95.32	10.642%	$105.464	$105.46	$105.45	$105.50
Purchase #3	$149.49	9.755%	$164.0727	$164.07	$164.05	$164.10
Purchase #4	$29.43	3.540%	$30.4718	$30.47	$30.45	$30.50
Purchase #5	$136.49	5.793%	$144.3969	$144.40	$144.40	$144.40
Purchase #6	$130.66	6.741%	$139.4678	$139.47	$139.45	$139.50
Purchase #7	$50.90	12.859%	$57.4452	$57.45	$57.45	$57.40
7 purchase totals =	$654.93		$705.9403	$705.94	$705.85	$706.00