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	$148.49	10.677%	$164.3443	$164.34	$164.35	$164.30
Purchase #2	$63.29	6.779%	$67.5804	$67.58	$67.60	$67.60
Purchase #3	$226.62	12.847%	$255.7339	$255.73	$255.75	$255.70
Purchase #4	$116.69	5.666%	$123.3017	$123.30	$123.30	$123.30
Purchase #5	$91.99	5.680%	$97.215	$97.22	$97.20	$97.20
Purchase #6	$177.89	13.243%	$201.448	$201.45	$201.45	$201.40
Purchase #7	$155.66	10.649%	$172.2362	$172.24	$172.25	$172.20
7 purchase totals =	$980.63		$1,081.8595	$1,081.86	$1,081.90	$1,081.70