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	$215.86	6.709%	$230.342	$230.34	$230.35	$230.30
Purchase #2	$215.90	5.391%	$227.5392	$227.54	$227.55	$227.50
Purchase #3	$91.53	8.294%	$99.1215	$99.12	$99.10	$99.10
Purchase #4	$112.26	3.632%	$116.3373	$116.34	$116.35	$116.30
Purchase #5	$54.31	12.677%	$61.1949	$61.19	$61.20	$61.20
Purchase #6	$123.95	10.817%	$137.3577	$137.36	$137.35	$137.40
Purchase #7	$238.78	3.126%	$246.2443	$246.24	$246.25	$246.20
7 purchase totals =	$1,052.59		$1,118.1369	$1,118.13	$1,118.15	$1,118.00