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	$87.82	4.329%	$91.6217	$91.62	$91.60	$91.60
Purchase #2	$106.51	9.490%	$116.6178	$116.62	$116.60	$116.60
Purchase #3	$225.57	11.666%	$251.885	$251.89	$251.90	$251.90
Purchase #4	$50.42	10.277%	$55.6017	$55.60	$55.60	$55.60
Purchase #5	$234.74	3.715%	$243.4606	$243.46	$243.45	$243.50
Purchase #6	$68.94	6.693%	$73.5542	$73.55	$73.55	$73.60
Purchase #7	$231.81	6.592%	$247.0909	$247.09	$247.10	$247.10
7 purchase totals =	$1,005.81		$1,079.8319	$1,079.83	$1,079.80	$1,079.90