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	$29.59	7.236%	$31.7311	$31.73	$31.75	$31.70
Purchase #2	$63.80	11.404%	$71.0758	$71.08	$71.10	$71.10
Purchase #3	$82.42	13.748%	$93.7511	$93.75	$93.75	$93.80
Purchase #4	$34.32	13.685%	$39.0167	$39.02	$39.00	$39.00
Purchase #5	$243.88	7.465%	$262.0856	$262.09	$262.10	$262.10
Purchase #6	$144.79	9.446%	$158.4669	$158.47	$158.45	$158.50
Purchase #7	$66.91	8.557%	$72.6355	$72.64	$72.65	$72.60
7 purchase totals =	$665.71		$728.7627	$728.78	$728.80	$728.80