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	$164.64	6.577%	$175.4684	$175.47	$175.45	$175.50
Purchase #2	$196.27	7.710%	$211.4024	$211.40	$211.40	$211.40
Purchase #3	$208.70	7.588%	$224.5362	$224.54	$224.55	$224.50
Purchase #4	$48.53	5.350%	$51.1264	$51.13	$51.15	$51.10
Purchase #5	$173.64	9.683%	$190.4536	$190.45	$190.45	$190.50
Purchase #6	$75.82	9.422%	$82.9638	$82.96	$82.95	$83.00
Purchase #7	$46.42	8.756%	$50.4845	$50.48	$50.50	$50.50
7 purchase totals =	$914.02		$986.4353	$986.43	$986.45	$986.50