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	$166.62	6.415%	$177.3087	$177.31	$177.30	$177.30
Purchase #2	$209.90	7.283%	$225.187	$225.19	$225.20	$225.20
Purchase #3	$118.85	6.841%	$126.9805	$126.98	$127.00	$127.00
Purchase #4	$27.51	13.732%	$31.2877	$31.29	$31.30	$31.30
Purchase #5	$164.87	7.243%	$176.8115	$176.81	$176.80	$176.80
Purchase #6	$164.78	4.870%	$172.8048	$172.80	$172.80	$172.80
Purchase #7	$94.78	9.222%	$103.5206	$103.52	$103.50	$103.50
7 purchase totals =	$947.31		$1,013.9008	$1,013.90	$1,013.90	$1,013.90