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	$72.32	13.410%	$82.0181	$82.02	$82.00	$82.00
Purchase #2	$33.48	8.472%	$36.3164	$36.32	$36.30	$36.30
Purchase #3	$84.43	11.799%	$94.3919	$94.39	$94.40	$94.40
Purchase #4	$31.93	4.838%	$33.4748	$33.47	$33.45	$33.50
Purchase #5	$126.32	3.873%	$131.2124	$131.21	$131.20	$131.20
Purchase #6	$31.80	13.334%	$36.0402	$36.04	$36.05	$36.00
Purchase #7	$103.88	10.323%	$114.6035	$114.60	$114.60	$114.60
7 purchase totals =	$484.16		$528.0573	$528.05	$528.00	$528.00