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	$220.88	8.175%	$238.9369	$238.94	$238.95	$238.90
Purchase #2	$169.68	13.776%	$193.0551	$193.06	$193.05	$193.10
Purchase #3	$168.47	7.366%	$180.8795	$180.88	$180.90	$180.90
Purchase #4	$82.81	12.695%	$93.3227	$93.32	$93.30	$93.30
Purchase #5	$58.64	4.746%	$61.4231	$61.42	$61.40	$61.40
Purchase #6	$187.89	13.730%	$213.6873	$213.69	$213.70	$213.70
Purchase #7	$98.27	7.357%	$105.4997	$105.50	$105.50	$105.50
7 purchase totals =	$986.64		$1,086.8043	$1,086.81	$1,086.80	$1,086.80