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	$73.49	12.461%	$82.6476	$82.65	$82.65	$82.60
Purchase #2	$217.49	9.515%	$238.1842	$238.18	$238.20	$238.20
Purchase #3	$126.78	6.549%	$135.0828	$135.08	$135.10	$135.10
Purchase #4	$74.46	8.822%	$81.0289	$81.03	$81.05	$81.00
Purchase #5	$38.29	6.161%	$40.649	$40.65	$40.65	$40.60
Purchase #6	$102.39	8.431%	$111.0225	$111.02	$111.00	$111.00
Purchase #7	$42.43	10.428%	$46.8546	$46.85	$46.85	$46.90
7 purchase totals =	$675.33		$735.4696	$735.46	$735.50	$735.40