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	$21.73	8.332%	$23.5405	$23.54	$23.55	$23.50
Purchase #2	$51.52	8.407%	$55.8513	$55.85	$55.85	$55.90
Purchase #3	$35.43	13.851%	$40.3374	$40.34	$40.35	$40.30
Purchase #4	$101.29	7.501%	$108.8878	$108.89	$108.90	$108.90
Purchase #5	$84.89	6.666%	$90.5488	$90.55	$90.55	$90.50
Purchase #6	$225.83	11.257%	$251.2517	$251.25	$251.25	$251.30
Purchase #7	$210.73	7.113%	$225.7192	$225.72	$225.70	$225.70
7 purchase totals =	$731.42		$796.1367	$796.14	$796.15	$796.10