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	$90.44	4.285%	$94.3154	$94.32	$94.30	$94.30
Purchase #2	$108.25	12.601%	$121.8906	$121.89	$121.90	$121.90
Purchase #3	$70.25	3.490%	$72.7017	$72.70	$72.70	$72.70
Purchase #4	$137.60	10.134%	$151.5444	$151.54	$151.55	$151.50
Purchase #5	$234.25	10.826%	$259.6099	$259.61	$259.60	$259.60
Purchase #6	$176.89	4.660%	$185.1331	$185.13	$185.15	$185.10
Purchase #7	$179.56	12.402%	$201.829	$201.83	$201.85	$201.80
7 purchase totals =	$997.24		$1,087.0241	$1,087.02	$1,087.05	$1,086.90