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	$204.85	10.850%	$227.0762	$227.08	$227.10	$227.10
Purchase #2	$78.52	11.565%	$87.6008	$87.60	$87.60	$87.60
Purchase #3	$54.51	12.636%	$61.3979	$61.40	$61.40	$61.40
Purchase #4	$221.77	9.801%	$243.5057	$243.51	$243.50	$243.50
Purchase #5	$197.28	10.286%	$217.5722	$217.57	$217.55	$217.60
Purchase #6	$178.54	12.298%	$200.4968	$200.50	$200.50	$200.50
Purchase #7	$43.39	13.496%	$49.2459	$49.25	$49.25	$49.20
7 purchase totals =	$978.86		$1,086.8955	$1,086.91	$1,086.90	$1,086.90