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	$152.60	10.434%	$168.5223	$168.52	$168.50	$168.50
Purchase #2	$126.32	13.359%	$143.1951	$143.20	$143.20	$143.20
Purchase #3	$57.68	6.381%	$61.3606	$61.36	$61.35	$61.40
Purchase #4	$22.27	11.674%	$24.8698	$24.87	$24.85	$24.90
Purchase #5	$240.82	10.236%	$265.4703	$265.47	$265.45	$265.50
Purchase #6	$77.44	7.744%	$83.437	$83.44	$83.45	$83.40
Purchase #7	$95.47	7.261%	$102.4021	$102.40	$102.40	$102.40
7 purchase totals =	$772.60		$849.2572	$849.26	$849.20	$849.30