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	$181.96	10.388%	$200.862	$200.86	$200.85	$200.90
Purchase #2	$78.98	13.155%	$89.3698	$89.37	$89.35	$89.40
Purchase #3	$182.80	11.280%	$203.4198	$203.42	$203.40	$203.40
Purchase #4	$51.38	13.738%	$58.4386	$58.44	$58.45	$58.40
Purchase #5	$207.34	4.466%	$216.5998	$216.60	$216.60	$216.60
Purchase #6	$95.72	6.673%	$102.1074	$102.11	$102.10	$102.10
Purchase #7	$70.84	8.863%	$77.1185	$77.12	$77.10	$77.10
7 purchase totals =	$869.02		$947.9159	$947.92	$947.85	$947.90