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	$219.51	10.417%	$242.3764	$242.38	$242.40	$242.40
Purchase #2	$60.51	4.659%	$63.3292	$63.33	$63.35	$63.30
Purchase #3	$104.88	12.774%	$118.2774	$118.28	$118.30	$118.30
Purchase #4	$198.40	5.453%	$209.2188	$209.22	$209.20	$209.20
Purchase #5	$164.88	13.160%	$186.5782	$186.58	$186.60	$186.60
Purchase #6	$104.60	6.217%	$111.103	$111.10	$111.10	$111.10
Purchase #7	$225.76	9.874%	$248.0515	$248.05	$248.05	$248.10
7 purchase totals =	$1,078.54		$1,178.9345	$1,178.94	$1,179.00	$1,179.00