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	$134.26	12.815%	$151.4654	$151.47	$151.45	$151.50
Purchase #2	$156.32	12.871%	$176.4399	$176.44	$176.45	$176.40
Purchase #3	$124.72	6.690%	$133.0638	$133.06	$133.05	$133.10
Purchase #4	$45.65	11.342%	$50.8276	$50.83	$50.85	$50.80
Purchase #5	$88.71	13.495%	$100.6814	$100.68	$100.70	$100.70
Purchase #6	$134.42	7.459%	$144.4464	$144.45	$144.45	$144.40
Purchase #7	$22.76	5.139%	$23.9296	$23.93	$23.95	$23.90
7 purchase totals =	$706.84		$780.8541	$780.86	$780.90	$780.80