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	$204.40	6.480%	$217.6451	$217.65	$217.65	$217.60
Purchase #2	$90.44	7.540%	$97.2592	$97.26	$97.25	$97.30
Purchase #3	$67.83	9.833%	$74.4997	$74.50	$74.50	$74.50
Purchase #4	$127.47	4.119%	$132.7205	$132.72	$132.70	$132.70
Purchase #5	$212.45	13.711%	$241.579	$241.58	$241.60	$241.60
Purchase #6	$67.74	5.462%	$71.44	$71.44	$71.45	$71.40
Purchase #7	$200.69	7.326%	$215.3925	$215.39	$215.40	$215.40
7 purchase totals =	$971.02		$1,050.5360	$1,050.54	$1,050.55	$1,050.50