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	$77.75	10.784%	$86.1346	$86.13	$86.15	$86.10
Purchase #2	$89.32	10.323%	$98.5405	$98.54	$98.55	$98.50
Purchase #3	$168.30	6.867%	$179.8572	$179.86	$179.85	$179.90
Purchase #4	$66.65	9.111%	$72.7225	$72.72	$72.70	$72.70
Purchase #5	$80.42	3.602%	$83.3167	$83.32	$83.30	$83.30
Purchase #6	$27.46	7.843%	$29.6137	$29.61	$29.60	$29.60
Purchase #7	$118.48	11.451%	$132.0471	$132.05	$132.05	$132.00
7 purchase totals =	$628.38		$682.2323	$682.23	$682.20	$682.10