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	$132.89	7.483%	$142.8342	$142.83	$142.85	$142.80
Purchase #2	$225.99	9.327%	$247.0681	$247.07	$247.05	$247.10
Purchase #3	$200.72	4.340%	$209.4312	$209.43	$209.45	$209.40
Purchase #4	$174.37	3.773%	$180.949	$180.95	$180.95	$180.90
Purchase #5	$99.40	5.307%	$104.6752	$104.68	$104.70	$104.70
Purchase #6	$41.54	4.725%	$43.5028	$43.50	$43.50	$43.50
Purchase #7	$184.49	3.214%	$190.4195	$190.42	$190.40	$190.40
7 purchase totals =	$1,059.40		$1,118.8800	$1,118.88	$1,118.90	$1,118.80