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	$171.33	4.781%	$179.5213	$179.52	$179.50	$179.50
Purchase #2	$235.82	12.188%	$264.5617	$264.56	$264.55	$264.60
Purchase #3	$28.86	9.423%	$31.5795	$31.58	$31.60	$31.60
Purchase #4	$169.84	9.813%	$186.5064	$186.51	$186.50	$186.50
Purchase #5	$33.99	9.715%	$37.2921	$37.29	$37.30	$37.30
Purchase #6	$131.33	6.743%	$140.1856	$140.19	$140.20	$140.20
Purchase #7	$158.46	11.581%	$176.8113	$176.81	$176.80	$176.80
7 purchase totals =	$929.63		$1,016.4579	$1,016.46	$1,016.45	$1,016.50