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	$57.28	11.510%	$63.8729	$63.87	$63.85	$63.90
Purchase #2	$174.78	12.185%	$196.0769	$196.08	$196.10	$196.10
Purchase #3	$225.45	7.320%	$241.9529	$241.95	$241.95	$242.00
Purchase #4	$246.87	13.432%	$280.0296	$280.03	$280.05	$280.00
Purchase #5	$77.60	11.614%	$86.6125	$86.61	$86.60	$86.60
Purchase #6	$71.59	7.562%	$77.0036	$77.00	$77.00	$77.00
Purchase #7	$124.86	12.703%	$140.721	$140.72	$140.70	$140.70
7 purchase totals =	$978.43		$1,086.2694	$1,086.26	$1,086.25	$1,086.30