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	$57.45	9.586%	$62.9572	$62.96	$62.95	$63.00
Purchase #2	$116.97	13.320%	$132.5504	$132.55	$132.55	$132.60
Purchase #3	$171.58	5.841%	$181.602	$181.60	$181.60	$181.60
Purchase #4	$52.73	8.601%	$57.2653	$57.27	$57.25	$57.30
Purchase #5	$129.88	7.166%	$139.1872	$139.19	$139.20	$139.20
Purchase #6	$126.58	12.622%	$142.5569	$142.56	$142.55	$142.60
Purchase #7	$88.26	13.629%	$100.289	$100.29	$100.30	$100.30
7 purchase totals =	$743.45		$816.4080	$816.42	$816.40	$816.60