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	$61.84	9.304%	$67.5936	$67.59	$67.60	$67.60
Purchase #2	$97.97	7.579%	$105.3951	$105.40	$105.40	$105.40
Purchase #3	$164.94	6.331%	$175.3824	$175.38	$175.40	$175.40
Purchase #4	$249.86	12.775%	$281.7796	$281.78	$281.80	$281.80
Purchase #5	$63.36	5.103%	$66.5933	$66.59	$66.60	$66.60
Purchase #6	$123.48	5.438%	$130.1948	$130.19	$130.20	$130.20
Purchase #7	$194.88	10.522%	$215.3853	$215.39	$215.40	$215.40
7 purchase totals =	$956.33		$1,042.3241	$1,042.32	$1,042.40	$1,042.40