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	$5.33	9.445%	$5.8334	$5.83	$5.85	$5.80
Purchase #2	$93.32	13.287%	$105.7194	$105.72	$105.70	$105.70
Purchase #3	$37.72	12.468%	$42.4229	$42.42	$42.40	$42.40
Purchase #4	$15.72	7.245%	$16.8589	$16.86	$16.85	$16.90
Purchase #5	$222.95	9.364%	$243.827	$243.83	$243.85	$243.80
Purchase #6	$246.40	5.327%	$259.5257	$259.53	$259.55	$259.50
Purchase #7	$29.63	7.659%	$31.8994	$31.90	$31.90	$31.90
7 purchase totals =	$651.07		$706.0867	$706.09	$706.10	$706.00