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	$117.78	13.598%	$133.7957	$133.80	$133.80	$133.80
Purchase #2	$167.33	13.461%	$189.8543	$189.85	$189.85	$189.90
Purchase #3	$71.94	12.359%	$80.8311	$80.83	$80.85	$80.80
Purchase #4	$58.50	13.607%	$66.4601	$66.46	$66.45	$66.50
Purchase #5	$183.62	13.318%	$208.0745	$208.07	$208.05	$208.10
Purchase #6	$82.33	8.489%	$89.319	$89.32	$89.30	$89.30
Purchase #7	$180.70	5.387%	$190.4343	$190.43	$190.45	$190.40
7 purchase totals =	$862.20		$958.7690	$958.76	$958.75	$958.80